Distribution in plant ,substrate and leachate of paclobutrazol following application to containerized Nerium oleander L.seedlings

[ENG]Paclobutrazol(PBZ)is a retardant often used in potted ornamental plants to control their growth and compactness. The distribution in plant,substrate and leachate of PBZ applied to containerized oleander seedlings were studied after a single liquid drench application to the substrate surface(20mga.i.perplant) in a nursery dedicated to pot production in SE Spain. PBZ significantly reduced all growth parameters, providing more compact plants of good commercial value and confirming its ability to reduce the vertical growth of native oleander in the nursery. The level of PBZ residues in leaves washigh-erat the end of pot cultivation (156 days post PBZ application) than at the first sampling time(30 days after PBZ applica-tion), where as the level in stems decreased for the same period of time. PBZ residues in roots remained constant during the experimental period. The high level of PBZ residues detected in the substrate 30 days after application had decreased significantly(by67%) by the end of the experiment. A greater leaching fraction was detected for PBZ-treated seedlings and so a greater amount of PBZ was leached into the nursery soil with the irrigation water attheend of the experiment. This greater amount of PBZ leached into the soil represents an important way of contamination in the nursery and a substantial risk to the environment. [ESP] Paclobutrazol (PBZ) es un retardante del crecimiento frecuentemente utilizado en el cultivo de plantas ornamentales en maceta para el control de su crecimiento y compacidad. La distribución en el sustrato, planta y drenaje de PBZ aplicado a plántulas de adelfa en contenedor fue estudiada tras la aplicación de una única dosis a la superficie del sustrato de la maceta (20 mgi.a.por planta) en una plantación comercial de un vivero localizado en el Sureste de España. PBZ redujo significativamente todos los parámetros del crecimiento, proporcionando plantas más compactas de buen valor comercial y conformando su capacidad para reducir el fuerte crecimiento vertical de la adelfa nativa en el vivero. El nivel de residuos de PBZ en hojas resultó más elevado al final del ciclo de cultivo en maceta (156 días tras la aplicación) que a los 30 días de la aplicación, mientras que la cantidad de residuos presentes en el tallo disminuyó para el mismo periodo de tiempo. Los residuos de PBZ en las raíces permanecieron constantes durante todo el período experimental. El elevado contenido de residuos de PBZ detectadosen el sustrato 30 días después de la aplicación se redujo significativamente (enun 67%) al final del experimento. Una mayor fracción de drenaje fue detectada en las plántulas tratadas con PBZ, a la vez que una mayor cantidad de PBZ fue drenado en el suelo del vivero conjuntamente con el agua de riego al final del experimento. Esta mayor cantidad de PBZ drenado en el suelo representa una vía importante de contaminación en el vivero así como un riesgo importante de contaminación medioambiental.This research was supported by CICYT projects(AGL2005-05588-C02-1 and AGL2005-05588-C02-2)and by the Consejería de Agricultura y Agua de la Región de Murcia,program (UPCT-CEBAS-IMIDA 2005)

Digital implementation of the feedforward loop of the asymmetrical half-bridge converter for LED lighting applications

The Asymmetrical Half Bridge converter (AHBC) has proven to be a promising candidate for LED lighting applications. It provides high efficiency, galvanic isolation and, at the same time, its output filter can be very small and, therefore, easily implemented without electrolytic capacitor. On the other hand, its main drawback is its poor attainable bandwidth. In any ac-dc LED lighting application, the input voltage of the AHBC is provided by a Power Factor Corrector (PFC) converter which has to be also implemented without electrolytic capacitor in order to assure the long lifetime of the whole LED driver. As a consequence, its output voltage (input voltage of the AHBC) is affected by a low-frequency ripple. Due to the poor bandwidth of the AHBC, this voltage ripple will be transferred to the converter output voltage, leading to flickering. A possible solution is using a feedforward loop for cancelling the effect of this low-frequency ripple without affecting stability. Due to the complex and non-linear transfer function of the AHBC, any analog feedforward loop has to be tuned for a given operating point, leading to a poor performance (i.e., high flickering, high ripple) when the AHBC moves away from that point. Dimming, which is a very frequent requirement in many LED drivers, implies large variations of the output voltage and, consequently, moving away from the aforementioned operating point. In this paper, a digital feedforward loop is proposed in order to solve this problem. The digital implementation allows the feedforward loop to perfectly cancel the ripple under any condition (e.g., output voltage variation due to dimming). Besides, despite its complex transfer function, this digital feedforward loop has been designed and optimized for its implementation in small-size microcontrollers. Experimental results with a 40-W prototype prove the usefulness of the proposed feedforward loop and the validity of the equations used in the optimized desig

The voltage-controlled compensation ramp: A new waveshaping technique for power factor correctors

IEEE Applied Power Electronics Conference (APEC) (27. 2008. Austin, Texas)This paper deals with a new control method for Power Factor Correctors. Control is carried out by a standard IC controller for peak current-mode dc-dc converters, with only an additional compensation ramp generator and peak detector. Neither an analog multiplier nor an input voltage sensor is needed to achieve quasi-sinusoidal line waveforms, which makes this method very attractive. The method is similar to the one-cycle control method, but can be very easily adapted for use with topologies different to the boost converter, i.e. flyback, buck-boost, SEPIC Cuk and Zeta topologies. Moreover, as the line current is cycle-by-cycle controlled, the resulting input current feedback loop is extremely fast, thus allowing the use of this type of control with high frequency line

Active input current shaper without an electrolytic capacitor for retrofit lamps applications

The evolution of solid-state lighting technology has transformed traditional solutions in lighting. High-brightness light-emitting diodes (HB-LEDs) have become very attractive light sources due to their excellent characteristics, namely high efficiency, a long lifetime, and low maintenance. It is evident that HB-LED drivers must be durable and efficient in order to enjoy these advantages. Moreover, to replace incandescent bulbs, the ac-to-dc HB-LED driver must be simple and have low size and comply with international regulations (i.e., injecting low-frequency harmonics into the mains supply). With the last modifications regarding low-power lighting equipment (i.e., < 25 W), the authors have traditionally focused their efforts on increasing efficiency by sacrificing sinusoidal input current, yet all their solutions obviate the suppression of the traditional electrolytic capacitor of ac-to-dc converters, highlighting that this is the price to pay for a simple and low-size solution. This paper, however, puts forward the design of a simple and low-size ac-to-dc HB-LED driver for retrofit lamps without an electrolytic capacitor in order to extend its lifetime. The solution proposed here derives from a well-known technique used in the past, the active input current shaper (AICS), but without an electrolytic capacitor in this case. If the electrolytic capacitor of an AICS is removed, then low-frequency ripple arises at its intermediate dc bus, adding some distortion in the line input current over the proper natural one of an AICS. However, this addition is slight in comparison to the proper natural distortion of AICSs. Moreover, the low-frequency ripple at the intermediate bus is not transferred to the output with the help of the rapid output dynamic response of the AICS, which prevents flicker. This paper presents a theoretical analysis that guarantees a compromise between compliance with international regulations and the use of capacitor technologies other than the electrolytic design. Finally, a 24-W experimental prototype has been built and tested to validate the theoretical results presented in this paper.This work was supported by the Spanish Ministry of Education and Science under Project MINECO-13-DPI2013-47176-C2-2-R, by the Government of the Principality of Asturias under Project FC-15-GRUPIN14-143, and by European Regional Development Fund grants

Influencia de diferentes temperaturas de sustrato y concentraciones de ácido indolbutírico en el esquejado de Coriaria myrtifolia

Se estudia Coriaria myrtifolia Linn., especie autóctona de interés ecológico (fijadora de N), medicinal (coriamirtina en los frutos) y ornamental (uso en reforestación de zonas pobres en N y como verde de complemento en floristería y en jardinería). Se pretende mejorar su multiplicación por esqueje, mediante uso de ácido indolbutírico (AIB) como hormona favorecedora del enraizamiento que ya ha mostrado su efectividad en numerosas especies, entre ellas Nerium oleander (Kose, 2000), también autóctona del Mediterráneo.Trabajo financiado por los proyectos: MCYT-FEDER AGL2001-2249-C03-01 y AGL2000-052 CICYT-FEDER. Expresamos nuestro agradecimiento a la Dir. Gral. de Investigación y Transf. Tecnológica de la Consejería de Agricultura, Agua y Medio Ambiente de la Región de Murcia por su colaboración para la ejecución de este trabaj

Acción de las giberelinas en la generación de nuevos cormos de Gladiolus tristis var concolor

Trabajos anteriores muestran que especies naturalizadas de gladiolo pueden ser aprovechadas como flor cortada (López et al., 2002). El problema de su difusión estriva en que aunque se multiplican bien sexual y asexualmente, la tasa de multiplicación es baja en cuanto a número de cormos productores de varas florales de calidad, mientras que las semillas, con buen poder germinativo, tras su siembra generan un pequeño cormillo que necesitará alrededor de dos años más para constituir un cormo adulto

Reductor activo de armónicos sin condensador electrolítico aplicado a lámparas LED de sustitición

XXIV Seminario Anual de Automática, Electrónica Industrial e Instrumentación 2017 (SAAEI'17), Valencia (España)De todos son conocidas las bondades de los diodos emisores de luz (Light-Emiting Diodes, LEDs) para la iluminación: alta eficiencia, larga vida útil, bajo mantenimiento, etc. Para hacer extensibles estas ventajas a toda la luminaria, el convertidor encargado de la alimentación no puede limitar sus características, y ha de ser también eficiente y duradero. Además, en el caso concreto de las lámparas LED para la sustitución de bombillas incandescentes hay que añadir más requisitos: la necesidad de reducir los costes y el cumplimiento de la normativa vigente de inyección de armónicos de baja frecuencia en la red de distribución de alterna. Por lo tanto, se exige mucho del convertidor a diseñar. A raíz de las últimas modificaciones relativas a equipos de baja potencia que ha introducido la normativa, surge la posibilidad de aplicar una solución topológica presentada en el pasado, que puede reunir todas las especificaciones requeridas. Este artículo propone los Reductores de Armónicos Activos (RA2) sin condensador electrolítico [1] para el diseño del convertidor CA/CC en este tipo de luminarias, revisando esta familia de topologías y presentando modificaciones sobre las mismas para conseguir los objetivos preestablecidos. Finalmente, esta propuesta se validará a partir de las pruebas realizadas sobre un prototipo de 24 W

Influencia del ciclo de cultivo y la conservación frigorífica en el color de la coliflor

La coliflor es un cultivo en aumento en la Región de Murcia, provocado principalmente por el incremento de su producción destinada a la exportación. Para mantener dicha cuota de exportación es necesaria la producción de una coliflor de gran calidad, requisito que cada vez más, aprecian los mercados nacionales. Esta calidad se basa fundamentalmente en su aspecto externo, donde el color de la pella es uno de los parámetros más importantes a tener en cuenta.Este trabajo ha sido financiando por el proyecto Séneca AGR/9/FS/9

A Family of High Frequency AC-LED Drivers Based on ZCS-QRCs

A family of dimmable AC-LED drivers fed from dc voltages, is presented in this paper based on Zero Current Switching Quasi-Resonant Converters (ZCS-QRCs). The proposed family of drivers is based on replacing the diode in conventional converter topologies (i.e. buck, boost or buck-boost) by a string of High-Brightness Light-Emitting Diodes (HB-LED). Hence, the HB-LED string will be working as the rectifier diode and the load, switching at the same frequency of the main switch. In this case, the output current, which is experimentally validated, shows a negative current peak due to the reverse-recovery effect of the HB-LEDs. In order to reduce the reverse-recovery effect on the HB-LEDs, the main switch of the proposed topologies is replaced with a full-wave resonant switch, which makes possible to reduce the di/dt during the turn-off of the HB-LED string, therefore the reverse recovery effect is eliminated. Moreover, the dimming of the HB-LEDs is done by means of changing the switching frequency of the converter, by varying the turn-off while keeping a constant turn-on time. In order to validate the analysis, the proposed topologies have been experimentally tested on a constructed prototype with an output power of 7.5