Search

The Maximum Power Point Tracking logic which regulates inverters in PV plants plays a fundamental role in order to obtain maximum power from PV modules array, despite of fluctuations of modules temperature and irradiance, both in grid connected and stand alone systems. Due to these fluctuations there is a continue variation of module electric performance. and so the inverter has to realize circuit condition which maximize PV plant power for that irradiance and modules temperature. A regulation system which doesn't fully optimize this situation, leads to an energy output certainly lower than declared; starting from commercial modules data sheets, in this work an evaluation of missing energy production has been performed, considering that power curve of PV modules decreases rapidly around its maximum point. Giving a gaussian distribution of regulation system mismatching, missing energy production has been evaluated vs different values of solar irradiance and corresponding functional parameters of PV module. Considering not negligible effect of module operating temperature, the missing power due to this factor has been evaluated too, considering that usually inverter regulation system doesn't neglects this operational parameter an woks considering module in standard temperature condition. Result are presented in a series of diagrams which allow a technical and economic evaluation of an hypothetic upgrade of inverter regulation system which would take into account all these fluctuations.

The aim of this paper is to investigate the characteristics of the atomization process of a liquid jet injected into a high-pressure air cross-flow, i.e. in condition similar to that occurring in the inlet duct of a LPP gas-turbine burner. The influences of controlling parameters such as air velocity, liquid velocity and diameter of the nozzle are considered. The main features of the spray morphology were determined by means of a tomographic visualization technique and the general evolution of the spray in some typical cases is presented in the paper. It is shown as the jet evolution is significantly influenced by the onset of a stripping atomization mechanism marked by the peculiar morphology of the spray cross-section. This is also evident from the observation of the jet trajectories determined by using a shadowgraphic technique. The different behavior of the atomization process induced by the stripping mechanism led to a bi-stable evolution of jet trajectory in dependence of the prevalence of the liquid or air velocities effects. This feature can be hardly modeled by the interpolating function proposed in the literature. As a consequence, a stronger effort to gain a deeper understanding of the fluid dynamic, involved in the jet break-up in presence of an air cross-flow, is still required in order to build-up a more realistic model of the jet trajectory evolution. (C) 2003 Published by Elsevier Science Inc.

A comparative analysis of the stability regimes of three different electrohydrodynamic atomization (electrospray) systems is presented. Availability of a high resolution imaging system allowed for a direct visualization of the breakup mechanisms. Both liquid flow rate and applied voltage are varied in a large grid of values in order to build up a database of the observable jet breakup regimes. The exploited conditions have been chosen with the purpose of evidencing the relative influences of geometrical, electrical and fluid_dynamical effects at various working conditions. Experimental results shed light on the complex interaction between the controlling parameters and resulted in the formulation of some necessary conditions for the occurrence of stable jet regimes. The final conclusion of the paper is the recognition of the actual limitation in the mass Row rate range where such regime can be stabilized. Nevertheless some suggestion comes for the exploitation of atomization condition different from the classical Taylor cone jet that could be successfully exploited either in combustion systems or other technological application. (C) 2000 Elsevier Science Inc. All rights reserved.

To verify the efficacy of botulinus toxin A (TB-A) in treating children with neuropathic bladder secondary to myelomeningocele (MMC) with detrusor hyperactivity/low compliance, resistance to pharmacological therapy, and candidates for enterocystoplasty.From January 2002 to June 2003, a group of 7 patients was selected (4 females, 3 males, mean age, 9.8 years, age range, 5-17 years) with detrusor hyperactivity, clean intermittent catheterization and resistance to pharmacological therapy. Two patients presented with grade 2-3 monolateral vesicoureteral reflux (VUR). All patients were incontinent despite catheterization. Botulinus toxin A was administered under general or local anesthesia by the injection of 200 IU of toxin diluted in 10 cc of physiologic solution with a metal or a flexible needle (3.7 F/21 GA). The needle was fully inserted into the detrusor muscle in about 20 sites, and 0.5 cc of solution were injected in each site, except the trigonum vesicae. Follow-up included ultrasound examination of the urinary tract and urodynamic studies performed at 6, 12 and 24 weeks and biannually thereafter. Micturition cystography was performed 3 months after the intervention. Urodynamic parameters were leak point pressure (LPP), leak point volume (LPV) and specific volume at 20 cm H2O pressure. The results were analyzed using the Wilcoxon test.A significant increase in LPV (range, 30-108%, mean, 77.6%) and in specific volume at 20 cm H2O pressure (CS 20) was observed in all patients. No significant change in LPP was found. One patient previously treated with the Cohen reimplantation technique experienced transient VUR which resolved spontaneously within 1 month. No major side effects from the injection of TB-A occurred. All patients were hospitalized for 24 hours with catheterization.The preliminary results in this small sample of patients suggest that the use of TB-A is efficacious in significantly improving urodynamic parameters and urine storage volume at low pressures in patients with neuropathic bladder resistant to pharmacological therapy.

Combustion processes evolving in mild conditions are correcterized by working temperature lower than the flame temperature of the traditional combustion systems, allowing for a drastic reduction of pollutant formation. Such operating conditions' need of specific plant configurations related to the recovery of flue gases generally used for diluting and preheating the reacting stream. The internal or external exhaust recirculation and the high mixing level with fresh feed needed in order to gain the "mild combustion" mode, present several technological problems. These problems are considered in this paper in relation to the feasibility of a reliable plant. It is demonstrated that the power consumption for the treatment of high temperature flue gases is in an acceptable range for working conditions characteristic of mild combustion. Complete and reduced models of methane oxidation have been considered in order to study the feasibility of batch and Well-Stirred Reactor (WSR) configurations. It is shown that a WSR is not only desirable for mild combustion but, also, that this reactor configuration is technologically interesting for a combustion process only if a high initial temperature (greater than 1000 K) and a very diluted condition (oxygen molar fraction of 0.05) are considered. Only in this case, residence times of practical interest are related to the suitable conversion level of reactants. The end of this paper discusses a fluid-dynamic configuration for a WSR operating in mild combustion mode.

The methodological aspects and the potentials of a quantitative imaging technique, suitable for the analysis of the condensed phases fields of diesel sprays in isothermal and burning conditions are described. The technique is based on the simultaneous detection of two polarized components of light scattered by the liquid fuel and/or the carbonaceous material present in a pulsed laser sheet, which crosses a diesel spray injected into a high pressure, high temperature environment. A couple of digital images are recorded: the first one is the pattern of the vertically polarized scattered light and it is used as descriptor of the scatterers concentration; the second one is the pattern of the ratio between two polarized components and it is used as descriptor or the scatterers characteristics Some representative images of these quantities are reported for preignition and post-ignition conditions. The level and the type of randomness of the condensed phases are very different for the two conditions. In...

We analyzed 7 mono-, 6 di- and 2 trinucleotide repeat loci in a well characterized series of 69 breast cancer cases, treated in the period 1985-1986 and followed for 12 years. Tumor-associated allele contractions or expansions were observed only at di- and trinucleotide repeats, and were detected in 14/69 cases (20%), of which 7 (10%) showed instability at 2 or more loci (10%). No alterations were detected at mononucleotide repeats known to be unstable in gastrointestinal tumors with the microsatellite mutator phenotype. Disease-free survival at 5 years, overall survival at 12 years of follow-up, tumor stage, estrogen/ progesteron receptor status, and expression of the Ki-67 proliferation marker were independent of microsatellite status.

The quantitative characterization of sooting flames in terms of soot load and total soot surface area continues to be a major challenge in both fundamental investigations and practical applications. More particularly, a major interest can be found to discriminate the two classes of particulate, namely soot and cenosphere, presents in power generation plants fuelled with heavy fuel oils. The Laser-Induced Incandescence (LII) technique is widely employed for the determination of soot volume fraction but LII may also be used to derive the particle diameter, profiting from the size-dependent cooling behavior of the laser-heated particles. The temporally resolved LII emissions has been successfully used in a heavy fuel oil spray flame to distinguish the two classes of carbonaceous panicles produced during the heavy fuel oil combustion. Moreover, it has been possible to follow along the flame axis the formation and bum-out of these two classes of particulate and their relative amount in terms of volume fraction.

The quantitative characterization of sooting flames in terms of soot load and total soot surface area continues to be a major challenge in both fundamental investigations and practical applications. More particularly, a major interest can be found to discriminate the two classes of particulate, namely soot and cenosphere, presents in power generation plants fuelled with heavy fuel oils. The Laser-Induced Incandescence (LII) technique is widely employed for the determination of soot volume fraction but LII may also be used to derive the particle diameter, profiting from the size-dependent cooling behavior of the laser-heated particles. The temporally resolved LII emissions has been successfully used in a heavy fuel oil spray flame to distinguish the two classes of carbonaceous panicles produced during the heavy fuel oil combustion. Moreover, it has been possible to follow along the flame axis the formation and bum-out of these two classes of particulate and their relative amount in terms of volume...

The interest to renewable energy sources for energy production is not new. The production of biomass is an alternative and relevant solution for using less fossil energy while preserving environment. Several studies have been conducted to qualify various oil and their blends from plants and vegetables as alternative renewable energy source. However, these studies were generally conducted with a test approach, without considering in detail all the aspects related to atomization, thermal stability and combustion characteristics of these fuels. The technical feasibility as a fuel of a typical vegetable oil, the rapeseed oil, has been already studied in heating plants, while the purpose of this study is to obtain more detailed information on the combustion performances of rapeseed oil and its emulsion with 9% ethyl alcohol in a pilot plant in comparison with diesel fuel.

An experimental study analyzing the complex relationship between external thermo fluid dynamic parameters and the ignition of diesel sprays, as well as flame propagation, is presented. The experiments were performed in a high-pressure, high-temperature system simulating the top dead center conditions in the combustion chamber of a diesel engine. The only simplification with respect to real diesel engines is relative to the aerodynamic pattern. In fact, in this case, the air flux is almost quiescent and does not influence significantly the spray evolution or the combustion behavior. The influences of two very different injection regimes on the autoignition characteristics of diesel sprays were investigated using imaging techniques. In order to perform this analysis, a careful choice of injection conditions, obtained with two different types of injection apparatus, was necessary. The spray evolution at both low and high temperatures (at the same air density), the temporal and spatial distributions of the ignition points, and the flame growth velocity were measured for the two cases. Analysis of the results revealed the specular behavior of the ignition spatial distributions in the two cases. A first attempt to correlate these different behaviors with the spray-flame interaction is presented, and its implications are discussed.

Isolates of Fusarium oxysporum were obtained from the vascular tissue of Phaseolus spp. and characterized by pathogenicity, vegetative compatibility, restriction fragment length polymorphisms (RFLPs), and random amplified polymorphic DNA (RAPD) analyses. Eleven isolates were F. oxysporum f. sp. phaseoli and comprised five pathogenic races. Two races, nine vegetative compatibility groups (VCGs), and three heterokaryon self-incompatible isolates are new reports for this forma specialis. Pathogenic and nonpathogenic isolates were not found in the same VCGs and, in some cases, there was a correspondence of VCG to race and place of origin. RFLPs with five different restriction enzymes and RAPD with four different primers indicated genetic diversity in F oxysporum f. sp. phaseoli. The banding patterns showed a correspondence to the VCGs, but not to the pathogenic races. RFLPs and RAPD markers could be used to distinguish isolates that were nonpathogenic, self-incompatible, and from obscure origins. The use of all four methods combined was effective in characterizing and providing insight into the complex relationship of F oxysporum f. sp. phaseoli.

This study describes a method for the detection of cucumber mosaic virus (CMV) by flow cytometry. Extracts from leaves of healthy and virus-infected plants were incubated with latex particles, washed, and then incubated in succession with rabbit anti-CMV antibodies and anti-rabbit immunoglobulin antibodies labeled with fluorescein. Adsorption of CMV virions on the latex particles allowed the virions to become visible to the laser of the cytometer. When the threshold value for virus detection was set at three times that of healthy controls, the detection limit of the cytofluorimetric method was 10 pg/ml of purified virions and that of the enzyme-linked immunosorbent assay (ELISA) was 2.5 ng/ml. The measuring range of the assay described here was 5 ng to 10 pg of purified virions and that of ELISA was 20 to 2.5 ng. The cytofluorimetric method detected the coat protein of CMV in the extract of two transgenic plants at a dilution of 10 -3 , while ELISA detected the viral protein at a dilution of 5 x 10 -2 . The assay was also used to detect plum pox potyvirus and potato virus Y, alone as well as concurrently with CMV.

The immunological tolerance technique was used to produce antisera able to differentiate between two formae speciales (lycopersici and Gliamhe) of Fusarium oxysporum. Induction of tolerance was obtained in C57BL/6 mice that at birth received soluble mycelial extract through lactation. Offspring of mothers injected intravenously within 12 h after delivery with 1 mg of protein of F. oxysporum f. sp. lycopersici extract, isolate 1110, were immunized with the extract (100 μg of protein) of F. oxysporum f. sp. dianthi, isolate 1111, 28, 35, 42, and 49 days after birth. Similarly, offspring of mothers injected with F. o. dianthi, isolate 1 111, were immunized with F. o. lycopersici, isolate 1110 [...]

Sprays generated from light oils with different chemical compositions were studied in isothermal and burning conditions, employing Laser Light Scattering and Extinction Measurements. Light Cyclic Oil (LCO) has an aromatic character, low viscosity and high volatility; Dewaxed oil (DEW) which contains noticeable amounts of polar-aromatic compounds, is very viscous and has a high boiling; Light oil (GL) has paraffinic characteristics and intermediate viscosity and volatility; Reference oil (GR) was a typical commercial light oil for domestic heating. Scattering coefficients of polarized light QVV and QHH were measured at θ=90° and θ=67° and compared with the Lorenz-Mie results for large transparent and absorbing spheres (droplets) and for small highly absorbing ones (soot particles). The average size of the droplets was determined in isothermal sprays employing the polarization ratio γ=QHH/QVV at θ=90° and θ=67° and it is found that the droplets size correlates well with the fuel viscosity. Combined measurements of γ(90°) and γ(67°) allowed the simultaneous determination of droplet average size and complex refractive index inside sprays in burning conditions, thus giving information on spray vaporization and liquid phase pyrolysis effects. When both droplets and soot particles coexist in the scattering volume γ(90°) is a signature of residual droplets in regions containing soot and γ(67°) is an indiactor of the presence of small concentrations of soot particles inside the evaporating spray region. The concentration of soot in its formation zone is maximum for the LCO aromatic fuel and minimum for the GL paraffinic one, thus showing that in swirled spray flames soot formation is also chemical kinetically controlled.

Vertical unconfined spray diesel oil flames was generated on a variable swirl burner with 90 KW power. 90° laser light scattering was employed to distinguish the fuel droplets and soot particles in the first part of the flames. Local values of the OH emission at ?=309.0 nm and of the ?=632.8 nm extinction and emission coefficients in the same region were obtained by Abel inverted chordal measurements. Profiles of soot particle size and number concentrations were obtained from scatter-extinction ratios, assuming a monodisperse spherical model; soot temperature distribution were evaluated by the Kirchhoff law. A new thermogravimetric technique, employed on the material sampled in the upper part of the flames, allowed quantitative distinction among the unburnt fuel, the heavy molecular mass products and the carbonaceous matrix. Flame development and spray penetration are studied to show the potentialities of laser light scattering and the thermogravimetric analysis. The results indicate that the two techniques can both detect and distinguish the fuel and soot particles, but they operate in different ranges of the droplet and soot volume fractions. © 1981 Combustion Institute.