Indoor characterization at production sccale: 200 kWp of CPV solar simulator measurements

In order to complement ISFOC’s characterization capabilities, a Helios 3198 CPV Solar Simulator was installed in summer 2010. This Solar Simulator, based on a parabolic mirror and a high-intensity, small area Xenon flash lamp was developed by the Instituto de Energía Solar in Madrid [1] and is manufactured and distributed by Soldaduras Avanzadas [2]. This simulator is used not only for R&D purposes, but as a quality control tool for incoming modules that are to be installed in ISFOC’s CPV plants. In this paper we will discuss the results of recent measurements of close to 5000 modules, the entire production of modules corresponding to a small CPV power plant (200 kWp). We scrutinize the resultant data for signs of drift in the measurements, and analyze the light quality before and after, to check for changes in spectrum or spatial uniformity.)

Circuito de disparo de lámparas flash para la iluminación de sistemas fotovoltaicos

La medición y testeo de células fotovoltaicas en el laboratorio o en la industria exige reproducir unas condiciones de iluminación semejantes a las reales. Por eso se utilizan sistemas de iluminación basados en lámparas flash de Xenon que reproducen las condiciones reales en cuanto a nivel de irradiancia y espectro de la luz incidente. El objetivo de este proyecto es realizar los circuitos electrónicos necesarios para el disparo de dichas lámparas. El circuito de alimentación y disparo de una lámpara flash consta de una fuente de alimentación variable, un circuito de disparo para la ionización del gas Xenon y la electrónica de control. Nuestro circuito de disparo pretende producir pulsos adecuados para los dispositivos fotovoltaicos tanto en irradiancia, espectro y en duración, de forma que con un solo disparo consigamos el tiempo, la irradiancia y el espectro suficiente para el testeo de la célula fotovoltaica. La mayoría de estos circuitos exceptuando los específicos que necesita la lámpara, serán diseñados, simulados, montados en PCB y comprobados posteriormente en el laboratorio. ABSTRACT. Measurement and testing of photovoltaic cells in the laboratory or in industry requires reproduce lighting conditions similar to the real ones. So are used based lighting systems xenon flash lamps that reproduce the actual conditions in the level of irradiance and spectrum of the incident light. The objective of this project is to make electronic circuits required for such lamps shot. The power supply circuit and flash lamp shot consists of a variable power supply, a trigger circuit for Xenon gas ionization and the control electronics. Our shot circuit aims to produce pulses suitable for photovoltaic devices both irradiance, spectrum and duration, so that with a single shot get the time, the irradiance and spectrum enough for testing the photovoltaic cell. Most of these circuits except lamp specific requirements will be designed, simulated, and PCB mounted subsequently tested in the laboratory.

In vivo magnetic resonance vascular imaging using laser-polarized 3He microbubbles

Laser-polarized gases (3He and 129Xe) are currently being used in magnetic resonance imaging as strong signal sources that can be safely introduced into the lung. Recently, researchers have been investigating other tissues using 129Xe. These studies use xenon dissolved in a carrier such as lipid vesicles or blood. Since helium is much less soluble than xenon in these materials, 3He has been used exclusively for imaging air spaces. However, considering that the signal of 3He is more than 10 times greater than that of 129Xe for presently attainable polarization levels, this work has focused on generating a method to introduce 3He into the vascular system. We addressed the low solubility issue by producing suspensions of 3He microbubbles. Here, we provide the first vascular images obtained with laser-polarized 3He. The potential increase in signal and absence of background should allow this technique to produce high-resolution angiographic images. In addition, quantitative measurements of blood flow velocity and tissue perfusion will be feasible.

Structural Characterization of Micro- and Mesoporous Carbon Materials Using In Situ High Pressure 129Xe NMR Spectroscopy

In situ high pressure 129Xe NMR spectroscopy in combination with volumetric adsorption measurements were used for the textural characterization of different carbon materials with well-defined porosity including microporous carbide-derived carbons, ordered mesoporous carbide-derived carbon, and ordered mesoporous CMK-3. Adsorption/desorption isotherms were measured also by NMR up to relative pressures close to p/p0 = 1 at 237 K. The 129Xe NMR chemical shift of xenon adsorbed in porous carbons is found to be correlated with the pore size in analogy to other materials such as zeolites. In addition, these measurements were performed loading the samples with n-nonane. Nonane molecules preferentially block the micropores. However, 129Xe NMR spectroscopy proves that the nonane also influences the mesopores, thus providing information about the pore system in hierarchically structured materials.

(Table 3) Noble gas composition of dissociated gas hydrate specimens from ODP Leg 164 sites

Fractionation of the noble gases should occur during formation of a Structure I gas hydrate from water and CH4 such that CH4 hydrate is greatly enriched in Xenon. Noble gas concentrations and fractionation factors (F[4He], F[22Ne], F[86Kr], and F[132Xe] as well as R/Ra) were determined for eight gas hydrate specimens collected on Leg 164 to evaluate this theoretical possibility and to assess whether sufficient quantities of Xe are hosted in oceanic CH4 hydrate to account for Xe "missing" from the atmosphere. The simplest explanation for our results is that samples contain mixtures of air and two end-member gases. One of the end-member gases is depleted in Ne, but significantly enriched in Kr and Xe, as anticipated if the source of this gas involves fractionation during Structure I gas hydrate formation. However, although oceanic CH4 hydrate may be greatly enriched in Xe, simple mass balance calculations indicate that oceanic CH4 hydrate probably represents only a minor reservoir of terrestrial Xe. Noble gas analyses may play an important role in understanding the dynamics of gas hydrate reservoirs, but significantly more work is needed than presented here.

Determining tetrafluoroborates : an evaluation of the fluoroborate anion selective electrode /

Mode of access: Internet.

Study of the effects of fluoride on teeth of children in Cleveland Public Schools /

Mode of access: Internet.

Fluoride in Illinois : sources, environmental and health effects, and a proposed ambient standard /

Bibliograhy: p. 71-84.

Corrosion behaviour of magnesium in ethylene glycol

Corrosion of magnesium engine components by coolant is an important issue in the automotive industry where magnesium alloys may be used. It is of significance to understand the corrosion behaviour of pure magnesium in ethylene glycol solutions, as this can provide a basis for developing new coolants for magnesium alloy engine blocks. In this paper, through corrosion and electrochemical tests, it was found that the corrosion rate of magnesium decreased with increasing concentration of ethylene glycol. Individual contaminants, such as NaCl, NaHCO3, Na2SO4 and NaCl can make aqueous ethylene glycol solution more corrosive to magnesium. However, in NaCl contaminated ethylene glycol, NaHCO3 and Na2SO4 showed some inhibition effect. The solution resistivity played an important role in the corrosion of magnesium in ethylene glycol solutions, and the competitive adsorption of ethylene glycol and the contaminants on the magnesium surface was also responsible for the observed corrosion behaviours. The corrosion of magnesium in ethylene glycol can be effectively inhibited by addition of fluorides that react with magnesium and form a protective film on the surface. (C) 2003 Elsevier Ltd. All rights reserved.

Effect of surface-perturbed intermolecular interaction on adsorption of simple gases on a graphitized carbon surface

In this paper, we investigate the effect of the solid surface on the fluid-fluid intermolecular potential energy. This modified fluid-fluid interaction energy due to the inducement of a solid surface is used in the grand canonical Monte Carlo (GCMC) simulation of various noble gases, nitrogen, and methane on graphitized thermal carbon black. This effect is such that the effective interaction potential energy between two particles close to surface is less than the potential energy if the solid substrate is not present. With this modification the GCMC simulation results agree extremely well with the experimental data over a wide range of pressures while the simulation results with the unmodified potential energy give rise to a shoulder near the neighborhood of monolayer coverage and the significant overprediction of the second and higher layer coverages. In particular the unmodified GCMC results exhibit very sharp change in those higher layers while the experimental data have a much gradual change in the uptake. We will illustrate this theory with adsorption data of argon, xenon, neon, nitrogen, and methane on graphitized thermal carbon black.

Effects of potential models in the vapor-liquid equilibria and adsorption of simple gases on graphitized thermal carbon black

In this paper, we investigate the effects of various potential models in the description of vapor–liquid equilibria (VLE) and adsorption of simple gases on highly graphitized thermal carbon black. It is found that some potential models proposed in the literature are not suitable for the description of VLE (saturated gas and liquid densities and the vapor pressure with temperature). Simple gases, such as neon, argon, krypton, xenon, nitrogen, and methane are studied in this paper. To describe the isotherms on graphitized thermal carbon black correctly, the surface mediation damping factor introduced in our recent publication should be used to calculate correctly the fluid–fluid interaction energy between particles close to the surface. It is found that the damping constant for the noble gases family is linearly dependent on the polarizability, suggesting that the electric field of the graphite surface has a direct induction effect on the induced dipole of these molecules. As a result of this polarization by the graphite surface, the fluid–fluid interaction energy is reduced whenever two particles are near the surface. In the case of methane, we found that the damping constant is less than that of a noble gas having the similar polarizability, while in the case of nitrogen the damping factor is much greater and this could most likely be due to the quadrupolar nature of nitrogen.

The Corrosion Performance of Magnesium Alloy AM-SC1 in Automotive Engine Block Applications

The magnesium alloy AM-SC1 has been developed as a creep-resistant automotive engine block material. This paper outlines its corrosion performance under laboratory test conditions, considering corrosion on both the external and internal surfaces. This study found that AM-SC1 has a corrosion performance comparable to AZ91 when subjected to an aggressive salt-spray environment or in galvanic-coupling environments. This article further demonstrates that, with the appropriate selection of a commercially available engine coolant, the internal corrosion of AM-SC1 can be maintained at a tolerable level. In addition, internal corrosion resistance can be significantly improved by the addition of fluorides to the coolant solution. It is concluded that AM-SC1 can be successfully used in an engine environment provided that some simple corrosion-prevention strategies are adopted.

The characterisation of clean metal surfaces

The most perfectly structured metal surface observed in practice is that of a field evaporated field-ion microscope specimen. This surface has been characterised by adopting various optical analogue techniques. Hence a relationship has been determined between the structure of a single plane on the surface of a field-ion emitter and the geometry of a binary zone plate. By relating the known focussing properties of such a zone plate to those obtained from the projected images of such planes in a field-ion micrograph, it is possible to extract new information regarding the local magnification of the image. Further to this, it has been shown that the entire system of planes comprising the field-ion imaging surface may be regarded as a moire pattern formed between over-lapping zone plates. The properties of such moire zone plates are first established in an analysis of the moire pattern formed between zone plates on a flat surface. When these ideas are applied to the field-ion image it becomes possible to deduce further information regarding the precise topography of the emitter. It has also become possible to simulate differently proJected field-ion images by overlapping suitably aberrated zone plates. Low-energy ion bombardment is an essential preliminary to much surface research as a means of producing chemically clean surfaces. Hence it is important to know the nature and distribution of the resultant lattice damage, and the extent to which it may be removed by annealing. The field-ion microscope has been used to investigate such damage because its characterisation lies on the atomic scale. The present study is concerned with the in situ sputtering of tungsten emitters using helium, neon, argon and xenon ions with energies in the range 100eV to 1keV, together with observations of the effect of annealing. The relevance of these results to surface cleaning schedules is discussed.