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Seeds germination of tart yellow passion fruit as influenced by heat treatment. = Germina o de sementes de maracujá amarelo azedo em fun o de tratamentos térmicos.
Marina Keiko Welter,Oscar José Smiderle,Sandra Cátia Pereira Uch?a,Miguel Torres Chang
Agro@mbiente On-line , 2011,
Abstract: The study aimed to determine the effects of heat treatments applied to seeds of bitter yellow passionfruit (/Passiflora edulis/ Sims f. flavicarpa DEG) in the uniformity of seed germination. The experimental design was completely randomized blocks under a factorial scheme (3 x 2) +1, the factors being temperature (40, 50 and 60°C) and time of water immersion (10 and 15 minutes) plus a control (ambient temperature), with four replicates. The characteristics evaluated were: percentage of germination and speed of germination, being obtained both accumulated germination within 13 days and average germination velocity index. Concerning to cumulative germination percentage, treatments can be grouped into three groups as follows: first group, treatment T1D2 with 74.5%; second group with treatments T0, T1D1 and T2D2 with 55%, 53% and 52.5% respectively; third group with treatments T2D1, T3D1 and T3D2 with 35.5%, 17% and 13.5% respectively. Treatment with bitter passion fruit seed immersion in water heated to 40 oC for 15 minutes showed 75% germination and a better uniformity of seedlings.
Numerical Simulation of an Argon Stirred Ladle with Top and Bottom Injection  [PDF]
Sofia Torres, Miguel A. Barron
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.613075
Abstract: The stirring of a molten steel ladle with argon injection through a top submerged lance and a bottom nozzle is numerically studied here through Computational Fluid Dynamics (CFD) simulations. Three lance submergence depths and three injection velocities are considered in the CFD numerical experiments. The turbulent dissipation rate is employed to characterize the stirring phenomenon. The mixing times are determined from the gas flow rate, ladle geometry and bath depth using an empirical correlation.
Inverter-Based Diesel Generator Emulator for the Study of Frequency Variations in a Laboratory-Scale Autonomous Power System  [PDF]
Miguel Torres, Luiz A. C. Lopes
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.53027
Abstract:

This paper presents the modeling, simulation and practical implementation of an inverter-based diesel generator emulator. The main purpose of this emulator is for the study of frequency variations in diesel-based autonomous power systems in a laboratory environment where the operation of a real diesel generator is not possible. The emulator basically consists in a voltage source inverter with a second order output filter which voltage references are given by the model of the diesel generator. The control of the emulator is based on the digital signal processor TMS320F2812, where the mathematical models of the diesel generator and the control of the inverter are computed in real-time. Parameters for the model were obtained from commercially available components. Experimental results for different values of speed droop showed that the emulator achieves a satisfactory performance in the transient and stationary response. For the stationary response, the measured frequency deviates from theoretical values with a mean absolute error of: 0.06 Hz for 0% droop, 0.037 Hz for 3% droop, and 0.087 Hz for 5% droop. For the transient response, the measured frequency nadir deviates from simulations in: 0.05 Hz for 0% droop, 0.02 Hz for 3% droop, and 0.1 Hz for 5% droop.

Virtual Synchronous Generator: A Control Strategy to Improve Dynamic Frequency Control in Autonomous Power Systems  [PDF]
Miguel Torres, Luiz A. C. Lopes
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.52A005
Abstract:

Ideally, diesel hybrid autonomous power systems would operate with high penetration of renewable energy sources such as wind and photovoltaic to minimize fuel consumption. However, since these are inherently intermittent and fluctuating, the grid-forming diesel engine generator sets are usually required to operate with larger amounts of spinning reserve, often at low loading conditions what tends to increases operating and maintenance costs. Frequency stability is of great concern in “small” systems, such as mini-grids, where any individual generator in-feed represents a substantial portion of the total demand. There, the initial rate of change of frequency is typically larger and a lower value of frequency can be reached in a shorter time than in conventional systems with all generation supplied by rotating machines, possibly resulting in under-frequency load shedding and tripping of renewable energy generators. The first part of this paper, discusses some general concepts regarding frequency stability in a diesel hybrid mini-grid and how energy storage systems can be used to enhance system performance. Then, a particular technique based on a virtual synchronous generator is presented and its effectiveness is demonstrated with simulation results.

A Virtual Synchronous Machine to Support Dynamic Frequency Control in a Mini-Grid That Operates in Frequency Droop Mode  [PDF]
Miguel Torres, Luiz A. C. Lopes
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.53025
Abstract:

This paper addresses the problem of dynamic frequency control in a diesel-based mini-grid. It is shown that a virtual synchronous machine (VSM) can support dynamic frequency control by adding virtual inertia and damping to the system. However, it is found that the typical formulation of damping power does not work properly when the grid forming gen-set operates in droop mode because of the unknown stabilization value of the grid frequency. As a solution to this problem, an estimator for the stabilization frequency that works in conjunction with the damping function of the VSM is proposed. Theoretical and experimental results provide evidence of a satisfactory performance of the proposed VSM with estimator for different values of the gen-set droop factor. The estimated stabilization frequency converges in approximately 2 s and the maximum frequency deviation during the transient is reduced in 34%, on average.

BioROM 2006
Miguel ángel Medina Torres
Panace@ : Revista de Medicina, Lenguaje y Traducción , 2006,
Abstract:
Manolo, no esta en la Junta? Manolo, Isn't in the Board of Directors?
Luis Miguel Torres
Revista de la Sociedad Espa?ola del Dolor , 2008,
Abstract:
Twin Peaks: Aproximación semiótica a la enunciación y recepción de una serie televisiva
Miguel Angel Torres Vitolas
La Mirada de Telemo , 2009,
Abstract:
LA DIVISION DE QUIMICA DE PRODUCTOS NATURALES DE LA SOCIEDAD CHILENA DE QUíMICA
MIGUEL RENE TORRES GAONA
Boletín de la Sociedad Chilena de Química , 2001,
Abstract:
EL PROBLEMA DE LA SOSTENIBILIDAD DENTRO DE LA COMPLEJIDAD DE LOS SISTEMAS DE PRODUCCION AGROPECUARIOS
Cotes Torres,Alejandro; Cotes Torres,José Miguel;
Revista Facultad Nacional de Agronomía, Medellín , 2005,
Abstract: the problem of sustainability is a topic that since the end of the xx century has been worrying more the different sectors of society; becoming one of the topics of greatest interest for managers, consumers, academics and investigators that conform the different agricultural food chains of the world. this paper presents from the general systems theory point of view some elements of critical reflection, approaching the problem of sustainability from the complexity of agricultural production systems, beginning with the original philosophical conception of agriculture and ending by outlining some considerations that should be kept in mind for the development of scientific and technological advances concordant with the agricultural food chain needs of the xxi century; which permit an orientation of not only work by professionals who lead the processes of animal and vegetable production, but also creates a sense of pertinence in all of the participants in the chain, highlighting the importance of studying by means of systemic thought, agronomy and animal science, as disciplines that approach to complexities of agriculture which is the angular stone of civilization, such as we know it at the moment.
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