A methodology for granularity-based control of parallelism in logic programs

Several types of parallelism can be exploited in logic programs while preserving correctness and efficiency, i.e. ensuring that the parallel execution obtains the same results as the sequential one and the amount of work performed is not greater. However, such results do not take into account a number of overheads which appear in practice, such as process creation and scheduling, which can induce a slow-down, or, at least, limit speedup, if they are not controlled in some way. This paper describes a methodology whereby the granularity of parallel tasks, i.e. the work available under them, is efficiently estimated and used to limit parallelism so that the effect of such overheads is controlled. The run-time overhead associated with the approach is usually quite small, since as much work is done at compile time as possible. Also,a number of run-time optimizations are proposed. Moreover, a static analysis of the overhead associated with the granularity control process is performed in order to decide its convenience. The performance improvements resulting from the incorporation of grain size control are shown to be quite good, specially for systems with medium to large parallel execution overheads.

Towards granularity based control of parallelism in logic programs

Several types of parallelism can be exploited in logic programs while preserving correctness and efficiency, i.e. ensuring that the parallel execution obtains the same results as the sequential one and the amount of work performed is not greater. However, such results do not take into account a number of overheads which appear in practice, such as process creation and scheduling, which can induce a slow-down, or, at least, limit speedup, if they are not controlled in some way. This paper describes a methodology whereby the granularity of parallel tasks, i.e. the work available under them, is efficiently estimated and used to limit parallelism so that the effect of such overheads is controlled. The run-time overhead associated with the approach is usually quite small, since as much work is done at compile time as possible. Also, a number of run-time optimizations are proposed. Moreover, a static analysis of the overhead associated with the granularity control process is performed in order to decide its convenience. The performance improvements resulting from the incorporation of grain size control are shown to be quite good, specially for systems with médium to large parallel execution overheads.

Efficient term size computation for granularity control

Knowing the size of the terms to which program variables are bound at run-time in logic programs is required in a class of optimizations which includes granularity control and recursion elimination. Such size is difficult to even approximate at compile time and is thus generally computed at run-time by using (possibly predeñned) predicates which traverse the terms involved. We propose a technique which has the potential of performing this computation much more efficiently. The technique is based on ñnding program procedures which are called before those in which knowledge regarding term sizes is needed and which traverse the terms whose size is to be determined, and transforming such procedures so that they compute term sizes "on the fly". We present a systematic way of determining whether a given program can be transformed in order to compute a given term size at a given program point without additional term traversal. Also, if several such transformations are possible our approach allows ñnding minimal transformations under certain criteria. We also discuss the advantages and applications of our technique (specifically in the task of granularity control) and present some performance results.

NetCDF based data archiving system applied to ITER Fast Plant System Control prototype

EURATOM/CIEMAT and Technical University of Madrid (UPM) have been involved in the development of a FPSC [1] (Fast Plant System Control) prototype for ITER, based on PXIe (PCI eXtensions for Instrumentation). One of the main focuses of this project has been data acquisition and all the related issues, including scientific data archiving. Additionally, a new data archiving solution has been developed to demonstrate the obtainable performances and possible bottlenecks of scientific data archiving in Fast Plant System Control. The presented system implements a fault tolerant architecture over a GEthernet network where FPSC data are reliably archived on remote, while remaining accessible to be redistributed, within the duration of a pulse. The storing service is supported by a clustering solution to guaranty scalability, so that FPSC management and configuration may be simplified, and a unique view of all archived data provided. All the involved components have been integrated under EPICS [2] (Experimental Physics and Industrial Control System), implementing in each case the necessary extensions, state machines and configuration process variables. The prototyped solution is based on the NetCDF-4 [3] and [4] (Network Common Data Format) file format in order to incorporate important features, such as scientific data models support, huge size files management, platform independent codification, or single-writer/multiple-readers concurrency. In this contribution, a complete description of the above mentioned solution is presented, together with the most relevant results of the tests performed, while focusing in the benefits and limitations of the applied technologies.

Digital Control Implementation to Reduce the Cost and Improve the Performance of the Control Stage of an Industrial Switched-Mode Power Supply

The main objective of this work is the design and implementation of the digital control stage of a 280W AC/DC industrial power supply in a single low-cost microcontroller to replace the analog control stage. The switch-mode power supply (SMPS) consists of a PFC boost converter with fixed frequency operation and a variable frequency LLC series resonant DC/DC converter. Input voltage range is 85VRMS-550VRMS and the output voltage range is 24V-28V. A digital controller is especially suitable for this kind of SMPS to implement its multiple functionalities and to keep the efficiency and the performance high over the wide range of input voltages. Additional advantages of the digital control are reliability and size. The optimized design and implementation of the digital control stage it is presented. Experimental results show the stable operation of the controlled system and an estimation of the cost reduction achieved with the digital control stage.

PWM Control of a Buck Converter with an Amorphous Core Coil

Pulse-width modulation is widely used to control electronic converters. One of the most topologies used for high DC voltage/low DC voltage conversion is the Buck converter. It is obtained as a second order system with a LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core instead of air core lets design converters with smaller size. If high switching frequencies are used for obtaining high quality voltage output, the value of the auto inductance L is reduced throughout the time. Then, robust controllers are needed if the accuracy of the converter response must not be affected by auto inductance and load variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a not-toohigh switching frequency is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results are presented.

Optimizing rabbit production under heat stress: cage density and cage size during fattening, and breeding system and water quality on rabbit does

The aim of this work was to evaluate different management strategies to optimize rabbit production under chronic heat stress. To achieve it, three trials were conducted. In the first trial, to find the optimal cage density in tropical very dry forest condition, were measured growth performance, mortality rate, injured animals and carcass performance over an initial population of 300 cross-breed rabbits of New Zealand, California, Butterfly, Dutch and Satin, weaned at 30 days (535 ± 8 g, standard error). Treatments evaluated were: 6, 12, 18 and 24 rabbits/m2 (3, 6, 9 and 12 rabbits/cage, respectively, each cage of 0.5 m2). The maximal temperature-humidity index indicated a severe heat stress from weaning to 2.2 kg body weight (experimental time). At the end of experimental period 10, 20, 30 and 30 rabbits from the treatments of 6, 12, 18 and 24 rabbits/m2, respectively, were slaughtered and carcass performance recorded. Average daily gain and feed intake decreased by 0.31 ± 0.070 and 1.20 ± 0.25 g, respectively, per each unit that the density increased at the beginning of the experiment (P = 0.001). It increased the length of the fattening period by 0.91 ± 0.16 d (P = 0.001) per each unit of increment of density. However, rabbit production (kg/m2) increased linear and quadratically with the density (P < 0.008). Animals housed at the highest density compared to the lower one tended to show a higher incidence of ringworm (68.9 vs 39.4%; P = 0.075), injured animals (16.8 vs 3.03%; P = 0.12) and mortality (20.5 vs 9.63%; P = 0.043). The proportion of scapular fat (P = 0.042) increased linearly with increasing levels of density. Increasing density reduced linearly dorsal length (P = 0.001), and reduced linear and quadratically drip loss percentage (P = 0.097 and 0.018, respectively). In the second trial, 46 nulliparous rabbit does (23 clipped and 23 unclipped) with a BW of 3.67 ± 0.05 kg (s.e.) were used to evaluate heat stress and circadian rhythms comparing unclipped and clipped rabbit does, and to study if a more extensive breeding system increase litters performance at weaning without impairing rabbit doe performance,. Rectal temperature, feed and water 4 intake were recorded for 24 h. Rabbit does were mated 7 d after circadian measurements, and randomly assigned to two breeding systems. Control (C): mated at 14 d after parturition + litter weaned at 35 d of age. Extensive (E): mate at 21 after parturition + litter weaned at 42 d of age. The first three cycles were evaluated concerning to rabbit doe and litter performance. Two hundred twenty eight weaned rabbits, were divided into two cage sizes: 0.5 and 0.25 m2 with same density (16 rabbit/m2) and growing performance was recorded. Farm and rectal temperatures were minimal and feed and water intake maximal during the night (P < 0.001). Unclipped rabbit does showed higher rectal temperature (P = 0.045) and lower feed intake respect to clipped does (P = 0.019) which suggest a lower heat stress in the latter. Kits weaned per litter was reduced by 33% (P=0.038) in C group. This reduction was more important in the 2nd and 3rd cycles compared to the first (P ≤ 0.054). Rabbit doe feed efficiency tended to decrease in E respect C group (P = 0.093), whereas it was impaired from the first to the third cycle by 48% (P = 0.014). Growing rabbits from the E group were heavier at weaning (by 38%. P < 0.001), showed a higher feed intake (+7.4%) and lower feed efficiency (-8.4%) throughout the fattening period (P ≤ 0.056) respect to C group. Cage size had minor influence in growing performance. In the third trial, forty five non pregnant and non lactating rabbit does (21 nulliparous and 24 multiparous) were assigned randomly to farm water and to potable water to study if a water quality improvement can affect positively rabbit doe response to heat stress during pregnancy and lactation. A transponder was implanted in each animal to record subcutaneous temperature at 07:30 and 14:30 h. Experimental period extended from pregnancy (with no lactation) to the next lactation (until day 28). Body temperature and milk production were recorded daily, and body condition, feed and water intake weekly. Water quality did not affect any trait (P ≥ 0.15). Pregnant rabbit does were classified as does that weaned (W: 47%), not weaned (NW: 44%) or those pregnant that did not deliver (NB: 9%). Body temperature and feed intake decreased during pregnancy (P ≤ 0.031), but water intake remained constant. In this period body temperature decreased with metabolic weight (P ≤ 0.009). In W and NW does, 5 from mating to birth energy and protein balance impaired (P≤0.011). Body temperature of W does tended to be the lowest (P ≤ 0.090). Pregnancy length and total number of kits born tended to be longer and higher in NW than in W does (P = 0.10 and 0.053, respectively). Kit mortality at birth and from birth to 14 d of lactation was high, being worse for NW than for W does (97 vs. 40%; P<0.001). Body temperature during lactation was maximal at day 12, and milk production increased it (P ≤ 0.025). . In conclusion, in our heat stress conditions densities higher than 18 rabbits/m2 (34 kg/m2) at the end of fattening, are not recommended despite cage size, gestation and lactation productivity impaired not only when lactation is extended and along successive reproductive cycles but also due to a reduced embryo/kit survival and finally water quality improvement did not attenuate negative effect of heat stress. RESUMEN El propósito de éste trabajo fue evaluar diferentes estrategias de manejo para optimizar la producción de conejos bajo estrés térmico. Para lo cual se desarrollaron tres experimentos. En el primer experimento, para encontrar el número óptimo de gazapos por m2 de jaula durante el cebo en condiciones de bosque muy seco tropical, se estudiaron los rendimientos durante el cebo, mortalidad, animales lesionados y rendimiento de la canal sobre una población inicial de 300 conejos mestizos de Nueva Zelanda, California, Mariposa, Holandés y Satin, destetados a los 30 días de edad (535 ± 8g, error estándar). Los tratamientos evaluados fueron: 6, 12, 18 y 24 conejos/m2 (3, 6, 9 y 12 conejos/jaula, respectivamente, en jaulas de 0.5 m2). Durante el período experimental (destete a 2.2 kg de peso vivo), se observaron valores de THI correspondientes con un estrés térmico severo (THI max. De 31 a 35). Al final del período experimental, 10, 20, 30, y 30 conejos de los tratamientos con densidades de 6, 12, 18 y 24 conejos/m2, respectivamente, fueron sacrificados y su canal fue valorada. El promedio de la ganancia diaria y el consumo de alimento disminuyeron en 0.31 ± 0.070 y 1.20 ± 0.25 g, respectivamente, por cada unidad de incremento en la densidad al inicio del experimento (P=0.001). Esto alargó el período de engorde en 0.91 ± 0.16 d (P=0.001) por cada unidad de incremento de la densidad. Sin embargo, la producción de conejos (kg/m2) aumentó lineal y cuadráticamente con la densidad (P<0.008). Los animales alojados en las mayores densidades en comparación con el resto tendieron a mostrar una mayore incidencia de tiña (68.9 vs 39.4%; P=0.075), de cantidad de animales heridos (16.8 vs 3.03%; P=0.12), así como de mortalidad (20.5 vs 9.63%; P=0.043). El aumento en la densidad aumentó linealmente la proporción de grasa escapular (P=0.042) y redujo linealmente la longitud dorsal (P=0.001), y lineal y cuadráticamente el porcentaje de pérdida por goteo (P=0.018). En el segundo experimento, 46 conejas nulliparas (23 rasuradas y 23 no rasuradas) con un peso vivo de 3.67 ± 0.05 kg (e.e.) fueron usadas para evaluar el estrés 8 térmico y los ritmos circadianos comparando conejas rasuradas o no, y estudiar si un sistema de crianza más extensivo mejora el desempeño de la camada al destete sin perjudicar la productividad de la coneja. Durante 24 h se midió la temperatura rectal, consumo de alimento y de agua. Las conejas fueron montadas 7 días después, y distribuidas en dos sistemas de crianza. El control (C): monta a 14 días posparto y destete a 35 d de edad. El extensivo (E): monta a 21 días posparto y destete a 42 d de edad. Se controló la productividad de la coneja y la camada durante los tres primeros ciclos. Doscientos veintiocho gazapos fueron distribuidos en dos tamaños de jaulas (0.5 y 0.25 m2) con la misma densidad (16 conejos/m2) y se controlaron sus rendimientos productivos. Durante la noche se observaron los valores mínimos para la temperatura ambiental y rectal, y los máximos para consumo de alimento y agua (P< 0.001). Las conejas no rasuradas mostraron mayor temperatura rectal (P=0.045) y menores valores de consumo de alimento con respecto a las conejas rasuradas (P=0.019), lo que sugiere un menor estrés térmico en las últimas. El número de gazapos destetados por camada se redujo en 33% (P=0.038) en el grupo C. Este comportamiento se acentuó en el 2do y 3er ciclo en comparación con el primero (P≤0.054). La eficiencia alimenticia de las conejas tendió a disminuir en el grupo E con respecto al grupo C (P=0.093), dicha tendencia se acentúa del primer al tercer ciclo en un 48% (P=0.014). Los gazapos en fase de crecimiento provenientes del grupo E fueron más pesados al momento del destete (en 38% P<0.001), mostrando un mayor consumo de alimento (+7.4%) y menor eficiencia alimenticia (-8.4%) a lo largo del engorde (P≤0.056) con respecto al grupo C. El tamaño de la jaula tuvo una mínima influencia en el comportamiento durante el crecimiento de éstos gazapos. En el tercer experimento, cuarenta y cinco conejas no gestantes ni lactantes (21 nulíparas y 24 multíparas) se les asignó al azar agua dos tipos de agua: común de la granja y agua potable, con el fin de estudiar si una mejora en la calidad del agua puede afectar positivamente la respuesta de la coneja al estrés térmico durante la gestación y la lactancia. Se les implantó un transponder para registrar la temperatura subcutánea a las 7:30 y a las 14:30 h. El período experimental se extendió desde la gestación (sin 9 lactancia) hasta la lactanción consecutiva (hasta los 28 días). La temperatura corporal y la producción de leche se controlaron diariamente, y la condición corporal, consumo de agua y alimento, semanalmente. La calidad del agua no afectó a ninguna variable (P≥0.15). Las conejas preñadas fueron clasificadas como conejas que destetaron (W: 47%), que no destetaron (NW:44%) o aquellas que no parieron (NB: 9%). La temperatura corporal y consumo de alimento disminuyeron durante la gestación (P≤0.031), mientras que el consumo de agua se mantuvo constante. La temperatura corporal descendió con el peso metabólico durante la gestación (P≤0.009). El balance de energía y proteína disminuyó desde la monta al parto para las conejas W y NW (P≤0.011). Durante la gestación la temperatura corporal tendió a ser menor en las conejas W (P≤0.090). La longitud de la gestación y el número total de gazapos nacidos tendieron a ser mayores en conejas NW que en conejas W (P=0.10 y 0.053, respectivamente). La mortalidad de los gazapos al parto y del parto a los 14 días de lactancia fue alta, siendo peor para las conejas NW que para las W (97 vs 40%; P<0.001). Durante la lactancia la temperatura corporal alcanzó su valor máximo para el día 12, y la producción de leche indujo un incremento en la misma (P≤0.025). En conclusión, en nuestras condiciones de estrés térmico y sin importar el tamaño de la jaula, no se recomiendan densidades mayores a 18 conejos/m2 (34 kg/m2) al final del engorde. La productividad de la gestación y la lactancia disminuyen cuando la lactancia es mayor y se suceden varios ciclos reproductivos seguidos. Esto se debe al efecto negativo del estrés térmico sobre la vitalidad y supervivencia del embrión/gazapo. La mejora de la calidad del agua atenuó el efecto negativo del estrés térmico. Las conejas más productoras parece que son aquéllas que consiguen manejar mejor el estrés térmico.

A technique for dynamic term size computation via program transformation

Knowing the size of the terms to which program variables are bound at run-time in logic programs is required in a class of applications related to program optimization such as, for example, granularity analysis and selection among different algorithms or control rules whose performance may be dependent on such size. Such size is difficult to even approximate at compile time and is thus generally computed at run-time by using (possibly predefined) predicates which traverse the terms involved. We propose a technique based on program transformation which has the potential of performing this computation much more efficiently. The technique is based on finding program procedures which are called before those in which knowledge regarding term sizes is needed and which traverse the terms whose size is to be determined, and transforming such procedures so that they compute term sizes "on the fly". We present a systematic way of determining whether a given program can be transformed in order to compute a given term size at a given program point without additional term traversal. Also, if several such transformations are possible our approach allows finding minimal transformations under certain criteria. We also discuss the advantages and applications of our technique and present some performance results.

Engineering metal precipitate size distributions to enhance gettering in multicrystalline silicon

The extraction of metal impurities during phosphorus diffusion gettering (PDG) is one of the crucial process steps when fabricating high-efficiency solar cells using low-cost, lower-purity silicon wafers. In this work, we show that for a given metal concentration, the size and density of metal silicide precipitates strongly influences the gettering efficacy. Different precipitate size distributions can be already found in silicon wafers grown by different techniques. In our experiment, however, the as-grown distribution of precipitated metals in multicrystalline Si sister wafers is engineered through different annealing treatments in order to control for the concentration and distribution of other defects. A high density of small precipitates is formed during a homogenization step, and a lower density of larger precipitates is formed during extended annealing at 740º C. After PDG, homogenized samples show a decreased interstitial iron concentration compared to as-grown and ripened samples, in agreement with simulations.

Excitación y control de IGBTs de un inversor trifásico sinusoidal

El origen del proyecto se encuentra en la mejora de un inversor trifásico sinusoidal comercial sobre la base del estudio de las técnicas de excitación óptimas para los IGBTs que lo componen en su etapa de potencia. En las primeras fases de planteamiento del proyecto se propone una idea mucho más ambiciosa, la realización de un nuevo convertidor de emergencia, destinado al sector ferroviario, para dar servicio de climatización. Este convertidor está formado por la asociación en cascada de un bloque DC/DC elevador y un bloque inversor DC/AC trifásico controlado mediante PWM con modulación sinusoidal. Se pretendía así dar solución a las siguientes problemáticas detectadas en los convertidores comercializados hasta el momento: un bloque elevador excesivamente sobredimensionado, subsistemas de control independientes para los dos bloques que configuran el convertidor, adicionalmente, la tarjeta driver se rediseña con cada cambio de especificaciones por parte de un nuevo cliente y finalmente, las comunicaciones tanto de diagnosis como de mantenimiento necesitaban una importante actualización. Inicialmente, se ha realizado un estudio teórico de los bloques elevador e inversor para poder realizar el diseño y dimensionamiento de sus componentes tanto semiconductores como electromagnéticos. Una vez completada la parte de potencia, se estudia el control que se realiza mediante medidas directas y simulación tanto de la estrategia de control del elevador como del inversor. Así se obtiene una información completa de la funcionalidad de las tarjetas existentes. Se desea realizar el diseño de una única tarjeta controladora y una única tarjeta de drivers para ambos bloques. Por problemas ajenos, en el transcurso de este proyecto se cancela su realización comercial, con lo que se decide al menos crear la placa de control y poder gobernar un convertidor ya existente, sustituyendo la tarjeta de control del bloque elevador. Para poder fabricar la placa de control se divide en dos tarjetas que irán conectadas en modo sándwich. En una tarjeta está el microcontrolador y en otra está todo el interface necesario para operar con el sistema: entradas y salidas digitales, entradas y salidas analógicas, comunicación CAN, y un pequeño DC/DC comercial que proporciona alimentación al prototipo. Se realiza un pequeño programa funcional para poder manejar el convertidor, el cual con una tensión de 110V DC, proporciona a la salida una tensión de 380V AC. Como ya se ha expuesto, debido a la cancelación del proyecto industrial no se profundiza más en su mejora y se decide proponerlo para su evaluación en su fase actual. ABSTRACT. The beginning of the project is found in the improvement of a commercial sine wave three phase inverter which is based in a study about optimal excitation techniques to IGBTs which compose in the power stage. In the early phases of project it is proposed a much more ambitious idea, the fact of a new emergency converter, proposed for the rail sector to work in an air condition unit. This converter is formed by an association of a block cascaded DC/DC booster and a block DC/AC inverter three-phase controlled by a sine wave modulation PWM. The purposed was to give a solution to following problems detected in commercial converters nowadays: an excessively oversized block boost, independent control subsystems for two blocks that configure the converter. In addition, driver board is redesigned with each specifications change demand it a new customer, and finally, the communications, diagnostic and maintenance that needed a important upgrade. Initially, it has been performed a theoretical study of boost and the inverter blocks to be able to perform the component’s design and the size (semiconductor and electromagnetic fields). Once finished power study, it is analysed the control performed using direct measures and simulation of boost control strategy and inverter. With this it is obtained complete information about existing cards functionality. The project is looking for the design of just one controller card and one drivers´ card for both blocks. By unrelated problems, during the course of this project a commercial realization. So at least its decided to create control board to be able to existing converter, replacing boost block’s control board. To be able to manufacture control board it is divided in two cards connected in sandwiching mode. In a card is microcontroller and in another is all needed interface to operate with the system: digital inputs and outputs, analogical inputs and outputs, CAN communication, and a small DC / DC business that provide power supply to the prototype. It is performed a small functional program to handle the converter, which with an input voltage 110V DC provides an output voltage 380V AC. As already has been exposed, due to industrial project cancellation it is decided no to continue with all improvements and directly to evaluate it in the current phase.

Effect of reservoir tillage on rainwater harvesting and soil erosion control under a developed rainfall simulator.

Soil erosion is a serious environmental threat in the Mediterranean region due to torrential rainfalls, and it contributes to the degradation of agricultural land. Techniques such as rainwater harvesting may improve soil water storage and increase agricultural productivity, which could result in more effective land usage. Reservoir tillage is an effective system of harvesting rainwater, but it has not been scientifically evaluated like other tillage systems. Its suitability for the conditions in Spain has not been determined. To investigate and quantify water storage from reservoir tillage and how it could be adapted to improve infiltration of harvested rainwater, a laboratory-scale rainfall simulator was developed. Rainfall characteristics, including rainfall intensity, spatial uniformity and raindrop size, confirm that natural rainfall conditions are simulated with sufficient accuracy. The simulator was auto-controlled by a solenoid valve and three pressure nozzles were used to spray water corresponding to five rainfall intensities ranging from 36 to 112 mm h-1 for 3 to 101-year return period with uniformity coefficients between 83 and 94%. In order to assess the reservoir tillage method under surface slopes of 0, 5, and 10%, three soil scooping devices with identical volume were used to make depressions in the following forms: a) truncated square pyramid, b) triangular prism, and c) truncated cone. These depressions were compared to a control soil surface with no depression. For the loam soil used in this study, results show that reservoir tillage was able to reduce soil erosion and surface runoff and significantly increase infiltration. There was significant difference between the depressions and the control. Compared to the control, depression (a) reduced surface runoff by about 61% and the sediment yield concentration by about 79%.

Effect of conservation tillage on soil physical properties, in-situ rainwater harvesting, and erosion control in arid and semi-arid regions

La escasez del agua en las regiones áridas y semiáridas se debe a la escasez de precipitaciones y la distribución desigual en toda la temporada, lo que hace de la agricultura de secano una empresa precaria. Un enfoque para mejorar y estabilizar el agua disponible para la producción de cultivos en estas regiones es el uso de tecnologías de captación de agua de lluvia in situ y su conservación. La adopción de los sistemas de conservación de la humedad del suelo in situ, tales como la labranza de conservación, es una de las estrategias para mejorar la gestión de la agricultura en zonas áridas y semiáridas. El objetivo general de esta tesis ha sido desarrollar una metodología de aplicación de labranza de depósito e investigar los efectos a corto plazo sobre las propiedades físicas del suelo de las diferentes prácticas de cultivo que incluyen labranza de depósito: (reservoir tillage, RT), la laboreo mínimo: (minimum tillage, MT), la no laboreo: (zero tillage, ZT) y laboreo convencional: (conventional tillage, CT) Así como, la retención de agua del suelo y el control de la erosión del suelo en las zonas áridas y semiáridas. Como una primera aproximación, se ha realizado una revisión profunda del estado de la técnica, después de la cual, se encontró que la labranza de depósito es un sistema eficaz de cosecha del agua de lluvia y conservación del suelo, pero que no ha sido evaluada científicamente tanto como otros sistemas de labranza. Los trabajos experimentales cubrieron tres condiciones diferentes: experimentos en laboratorio, experimentos de campo en una región árida, y experimentos de campo en una región semiárida. Para investigar y cuantificar el almacenamiento de agua a temperatura ambiente y la forma en que podría adaptarse para mejorar la infiltración del agua de lluvia recolectada y reducir la erosión del suelo, se ha desarrollado un simulador de lluvia a escala de laboratorio. Las características de las lluvias, entre ellas la intensidad de las precipitaciones, la uniformidad espacial y tamaño de la gota de lluvia, confirmaron que las condiciones naturales de precipitación son simuladas con suficiente precisión. El simulador fue controlado automáticamente mediante una válvula de solenoide y tres boquillas de presión que se usaron para rociar agua correspondiente a diferentes intensidades de lluvia. Con el fin de evaluar el método de RT bajo diferentes pendientes de superficie, se utilizaron diferentes dispositivos de pala de suelo para sacar un volumen idéntico para hacer depresiones. Estas depresiones se compararon con una superficie de suelo control sin depresión, y los resultados mostraron que la RT fue capaz de reducir la erosión del suelo y la escorrentía superficial y aumentar significativamente la infiltración. Luego, basándonos en estos resultados, y después de identificar la forma adecuada de las depresiones, se ha diseñado una herramienta combinada (sistema integrado de labranza de depósito (RT)) compuesto por un arado de una sola línea de chisel, una sola línea de grada en diente de pico, sembradora modificada, y rodillo de púas. El equipo fue construido y se utiliza para comparación con MT y CT en un ambiente árido en Egipto. El estudio se realizó para evaluar el impacto de diferentes prácticas de labranza y sus parámetros de funcionamiento a diferentes profundidades de labranza y con distintas velocidades de avance sobre las propiedades físicas del suelo, así como, la pérdida de suelo, régimen de humedad, la eficiencia de recolección de agua, y la productividad de trigo de invierno. Los resultados indicaron que la RT aumentó drásticamente la infiltración, produciendo una tasa que era 47.51% más alta que MT y 64.56% mayor que la CT. Además, los resultados mostraron que los valores más bajos de la escorrentía y pérdidas de suelos 4.91 mm y 0.65 t ha-1, respectivamente, se registraron en la RT, mientras que los valores más altos, 11.36 mm y 1.66 t ha-1, respectivamente, se produjeron en el marco del CT. Además, otros dos experimentos de campo se llevaron a cabo en ambiente semiárido en Madrid con la cebada y el maíz como los principales cultivos. También ha sido estudiado el potencial de la tecnología inalámbrica de sensores para monitorizar el potencial de agua del suelo. Para el experimento en el que se cultivaba la cebada en secano, se realizaron dos prácticas de labranza (RT y MT). Los resultados mostraron que el potencial del agua del suelo aumentó de forma constante y fue consistentemente mayor en MT. Además, con independencia de todo el período de observación, RT redujo el potencial hídrico del suelo en un 43.6, 5.7 y 82.3% respectivamente en comparación con el MT a profundidades de suelo (10, 20 y 30 cm, respectivamente). También se observaron diferencias claras en los componentes del rendimiento de los cultivos y de rendimiento entre los dos sistemas de labranza, el rendimiento de grano (hasta 14%) y la producción de biomasa (hasta 8.8%) se incrementaron en RT. En el experimento donde se cultivó el maíz en regadío, se realizaron cuatro prácticas de labranza (RT, MT, ZT y CT). Los resultados revelaron que ZT y RT tenían el potencial de agua y temperatura del suelo más bajas. En comparación con el tratamiento con CT, ZT y RT disminuyó el potencial hídrico del suelo en un 72 y 23%, respectivamente, a la profundidad del suelo de 40 cm, y provocó la disminución de la temperatura del suelo en 1.1 y un 0.8 0C respectivamente, en la profundidad del suelo de 5 cm y, por otro lado, el ZT tenía la densidad aparente del suelo y resistencia a la penetración más altas, la cual retrasó el crecimiento del maíz y disminuyó el rendimiento de grano que fue del 15.4% menor que el tratamiento con CT. RT aumenta el rendimiento de grano de maíz cerca de 12.8% en comparación con la ZT. Por otra parte, no hubo diferencias significativas entre (RT, MT y CT) sobre el rendimiento del maíz. En resumen, según los resultados de estos experimentos, se puede decir que mediante el uso de la labranza de depósito, consistente en realizar depresiones después de la siembra, las superficies internas de estas depresiones se consolidan de tal manera que el agua se mantiene para filtrarse en el suelo y por lo tanto dan tiempo para aportar humedad a la zona de enraizamiento de las plantas durante un período prolongado de tiempo. La labranza del depósito podría ser utilizada como un método alternativo en regiones áridas y semiáridas dado que retiene la humedad in situ, a través de estructuras que reducen la escorrentía y por lo tanto puede resultar en la mejora de rendimiento de los cultivos. ABSTRACT Water shortage in arid and semi-arid regions stems from low rainfall and uneven distribution throughout the season, which makes rainfed agriculture a precarious enterprise. One approach to enhance and stabilize the water available for crop production in these regions is to use in-situ rainwater harvesting and conservation technologies. Adoption of in-situ soil moisture conservation systems, such as conservation tillage, is one of the strategies for upgrading agriculture management in arid and semi-arid environments. The general aim of this thesis is to develop a methodology to apply reservoir tillage to investigate the short-term effects of different tillage practices including reservoir tillage (RT), minimum tillage (MT), zero tillage (ZT), and conventional tillage (CT) on soil physical properties, as well as, soil water retention, and soil erosion control in arid and semi-arid areas. As a first approach, a review of the state of the art has been done. We found that reservoir tillage is an effective system of harvesting rainwater and conserving soil, but it has not been scientifically evaluated like other tillage systems. Experimental works covered three different conditions: laboratory experiments, field experiments in an arid region, and field experiments in a semi-arid region. To investigate and quantify water storage from RT and how it could be adapted to improve infiltration of harvested rainwater and reduce soil erosion, a laboratory-scale rainfall simulator was developed. Rainfall characteristics, including rainfall intensity, spatial uniformity and raindrop size, confirm that natural rainfall conditions are simulated with sufficient accuracy. The simulator was auto-controlled by a solenoid valve and three pressure nozzles were used to spray water corresponding to different rainfall intensities. In order to assess the RT method under different surface slopes, different soil scooping devices with identical volume were used to create depressions. The performance of the soil with these depressions was compared to a control soil surface (with no depression). Results show that RT was able to reduce soil erosion and surface runoff and significantly increase infiltration. Then, based on these results and after selecting the proper shape of depressions, a combination implement integrated reservoir tillage system (integrated RT) comprised of a single-row chisel plow, single-row spike tooth harrow, modified seeder, and spiked roller was developed and used to compared to MT and CT in an arid environment in Egypt. The field experiments were conducted to evaluate the impact of different tillage practices and their operating parameters at different tillage depths and different forward speeds on the soil physical properties, as well as on runoff, soil losses, moisture regime, water harvesting efficiency, and winter wheat productivity. Results indicated that the integrated RT drastically increased infiltration, producing a rate that was 47.51% higher than MT and 64.56% higher than CT. In addition, results showed that the lowest values of runoff and soil losses, 4.91 mm and 0.65 t ha-1 respectively, were recorded under the integrated RT, while the highest values, 11.36 mm and 1.66 t ha -1 respectively, occurred under the CT. In addition, two field experiments were carried out in semi-arid environment in Madrid with barley and maize as the main crops. For the rainfed barley experiment, two tillage practices (RT, and MT) were performed. Results showed that soil water potential increased quite steadily and were consistently greater in MT and, irrespective of the entire observation period, RT decreased soil water potential by 43.6, 5.7, and 82.3% compared to MT at soil depths (10, 20, and 30 cm, respectively). In addition, clear differences in crop yield and yield components were observed between the two tillage systems, grain yield (up to 14%) and biomass yield (up to 8.8%) were increased by RT. For the irrigated maize experiment, four tillage practices (RT, MT, ZT, and CT) were performed. Results showed that ZT and RT had the lowest soil water potential and soil temperature. Compared to CT treatment, ZT and RT decreased soil water potential by 72 and 23% respectively, at soil depth of 40 cm, and decreased soil temperature by 1.1 and 0.8 0C respectively, at soil depth of 5 cm. Also, ZT had the highest soil bulk density and penetration resistance, which delayed the maize growth and decreased the grain yield that was 15.4% lower than CT treatment. RT increased maize grain yield about 12.8% compared to ZT. On the other hand, no significant differences among (RT, MT, and CT) on maize yield were found. In summary, according to the results from these experiments using reservoir tillage to make depressions after seeding, these depression’s internal surfaces are consolidated in such a way that the water is held to percolate into the soil and thus allowing time to offer moisture to the plant rooting zone over an extended period of time. Reservoir tillage could be used as an alternative method in arid and semi-arid regions and it retains moisture in-situ, through structures that reduce runoff and thus can result in improved crop yields.

Storage requirements for PV power ramp-rate control

Short-term variability in the power generated by large grid-connected photovoltaic (PV) plants can negatively affect power quality and the network reliability. New grid-codes require combining the PV generator with some form of energy storage technology in order to reduce short-term PV power fluctuation. This paper proposes an effective method in order to calculate, for any PV plant size and maximum allowable ramp-rate, the maximum power and the minimum energy storage requirements alike. The general validity of this method is corroborated with extensive simulation exercises performed with real 5-s one year data of 500 kW inverters at the 38.5 MW Amaraleja (Portugal) PV plant and two other PV plants located in Navarra (Spain), at a distance of more than 660 km from Amaraleja.

Effect of reservoir tillage on rainwater havesting and soil erosion control under a developed rainfall simulator

Soil erosion is a serious environmental threat in the Mediterranean region due to torrential rainfalls, and it contributes to the degradation of agricultural land. Techniques such as rainwater harvesting may improve soil water storage and increase agricultural productivity, which could result in more effective land usage. Reservoir tillage is an effective system of harvesting rainwater, but it has not been scientifically evaluated like other tillage systems. Its suitability for the conditions in Spain has not been determined. To investigate and quantify water storage from reservoir tillage and how it could be adapted to improve infiltration of harvested rainwater, a laboratory-scale rainfall simulator was developed. Rainfall characteristics, including rainfall intensity, spatial uniformity and raindrop size, confirm that natural rainfall conditions are simulated with sufficient accuracy. The simulator was auto-controlled by a solenoid valve and three pressure nozzles were used to spray water corresponding to five rainfall intensities ranging from 36 to 112 mm h− 1 for 3 to 101-year return period with uniformity coefficients between 83 and 94%. In order to assess the reservoir tillage method under surface slopes of 0, 5, and 10%, three soil scooping devices with identical volume were used to make depressions in the following forms: a) truncated square pyramid, b) triangular prism, and c) truncated cone. These depressions were compared to a control soil surface with no depression. For the loam soil used in this study, results show that reservoir tillage was able to reduce soil erosion and surface runoff and significantly increase infiltration. There was significant difference between the depressions and the control. Compared to the control, depression (a) reduced surface runoff by about 61% and the sediment yield concentration by about 79%.

Using the Cross-Entropy Method for Control Optimization: A Case Study of See-and-Avoid on Unmanned Aerial Vehicles

This paper presents an adaptation of the Cross-Entropy (CE) method to optimize fuzzy logic controllers. The CE is a recently developed optimization method based on a general Monte-Carlo approach to combinatorial and continuous multi-extremal optimization and importance sampling. This work shows the application of this optimization method to optimize the inputs gains, the location and size of the different membership functions' sets of each variable, as well as the weight of each rule from the rule's base of a fuzzy logic controller (FLC). The control system approach presented in this work was designed to command the orientation of an unmanned aerial vehicle (UAV) to modify its trajectory for avoiding collisions. An onboard looking forward camera was used to sense the environment of the UAV. The information extracted by the image processing algorithm is the only input of the fuzzy control approach to avoid the collision with a predefined object. Real tests with a quadrotor have been done to corroborate the improved behavior of the optimized controllers at different stages of the optimization process.