| 1. |
- Salome, Pedro M. P., et al.
(författare)
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A comparison between thin film solar cells made from co-evaporated CuIn1-xGaxSe2 using a one-stage process versus a three-stage process
- 2015
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Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 23:4, s. 470-478
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Tidskriftsartikel (refereegranskat)abstract
- Until this day, the most efficient Cu(In,Ga)Se-2 thin film solar cells have been prepared using a rather complex growth process often referred to as three-stage or multistage. This family of processes is mainly characterized by a first step deposited with only In, Ga and Se flux to form a first layer. Cu is added in a second step until the film becomes slightly Cu-rich, where-after the film is converted to its final Cu-poor composition by a third stage, again with no or very little addition of Cu. In this paper, a comparison between solar cells prepared with the three-stage process and a one-stage/in-line process with the same composition, thickness, and solar cell stack is made. The one-stage process is easier to be used in an industrial scale and do not have Cu-rich transitions. The samples were analyzed using glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, current-voltage-temperature, capacitance-voltage, external quantum efficiency, transmission/reflection, and photoluminescence. It was concluded that in spite of differences in the texturing, morphology and Ga gradient, the electrical performance of the two types of samples is quite similar as demonstrated by the similar J-V behavior, quantum spectral response, and the estimated recombination losses.
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| 2. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Salomé, Pedro M. P., et al.
(författare)
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Secondary crystalline phases identification in CuZnSnSe thin films : contributions from Raman scattering and photoluminescence
- 2014
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 49:21, s. 7425-7436
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present the Raman peak positions of the quaternary pure selenide compound CuZnSnSe (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, CuSnSe, ZnSe, SnSe, SnSe, MoSe and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials' model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.
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| 4. |
- Drummond, Miguel V., et al.
(författare)
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Tunable Optical Dispersion Compensator Based on Power Splitting Between Two Dispersive Media
- 2010
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 28:8, s. 1164-1175
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose and experimentally demonstrate a novel tunable optical dispersion compensator (TODC). Dispersion compensation is achieved by splitting the input signal between two dispersive media and adding the resulting signals thereafter. Tunable compensation is attained by controlling the power splitting ratio of the input signal between both dispersive media. The frequency response of the TODC is theoretically assessed considering signal addition in the optical and electrical domains. The latter case is enabled by using optical single side-band (OSSB) modulation, which allows preserving the phase information of dispersive media output signals after direct detection. This is the only case experimentally tested, since it avoids stability problems related with coherent addition of optical signals. A TODC with a tuning range of -340 to 0 ps/nm was designed and experimentally assessed for a 40 Gb/s nonreturn-to-zero OSSB signal. The tunable power splitter consisted of an automatic polarization controller and a polarization beam splitter, which offered a tuning time lower than 150 mu s. A bit error rate lower than 10(-8) was measured on the entire compensation range with a maximum power penalty of 3.3 dB relatively to an SSB signal in back-to-back.
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| 5. |
- Auer, Gunther, et al.
(författare)
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CELTIC CP5-026 WINNER+, D1.5 Intermediate Report on System Aspect of Advanced RRM
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The deliverable describes the second set of best innovations proposed in the framework of the WP1 on system aspect of advanced Radio Resource Management (RRM) approved by the System Group. These concepts consist of promising innovative techniques and include an initial evaluation of the performance and benefits as far as already available. A brief description of each technique together with the relevant state of the art is provided.Moreover, first considerations about the requirements on the system, especially regarding measurements, signalling, architecture and protocols are described. The last set of innovations will be ready for the final deliverable of proof of concept evaluation.
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| 6. |
- da Silva, Paulo S P, et al.
(författare)
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Release of carbon and nitrogen during pylolysis of reduced lignin black liquors : experimental results
- 2017
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Ingår i: International chemical recovery conference, May 24-26, 2017, Halifax, Canada.
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Konferensbidrag (refereegranskat)abstract
- Removing lignin from black liquor is of increasing industrial interest. It has the potential to create a new product stream for pulp mills as well as being a method for reducing the load of over-loaded recovery boilers. Currently, there is very little information on the combustion properties of reduced lignin black liquors. Of particular importance is the split of carbon and nitrogen. The carbon split is especially important because it plays an important role in how much carbon reaches the char bed. This in turn affects the lower furnace temperature, which plays an important role in reduction efficiency; sulfur and alkali release; and NO and cyanate formation. The nitrogen split is of interest because a part of the black liquor nitrogen precipitates with the lignin, potentially changing the behavior of black liquor N. The purpose of this work is to investigate the effect of lignin removal on carbon and nitrogen distribution between volatiles and char during pyrolysis. In this work, black liquors (one SW and one eucalyptus) with different levels of lignin removal were pyrolysed in a single particle furnace for 2 seconds at temperatures from 900°C to 1100°. Additional softwood and hardwood liquors were also pyrolyzed in order to study liquor to liquor variability. The carbon and nitrogen splits were obtained by analyzing the chars from the pyrolysis experiments using a CHNS elemental analyzer. Results show a similar carbon split for liquors with up to 25% lignin removal. The nitrogen split was also found to be fairly consistent with approximately 45% of the nitrogen staying with the char. This information has partly been used in another study in the CFD modeling of the combustion of black liquor with different levels of lignin removal.
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| 7. |
- Hantson, Stijn, et al.
(författare)
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The status and challenge of global fire modelling
- 2016
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 13:11, s. 3359-3375
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Tidskriftsartikel (refereegranskat)abstract
- Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central question underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. We indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP.
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| 8. |
- Nashih, Samuel K., et al.
(författare)
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Validation of a Simulation Model for Analysis of Shading Effects on Photovoltaic Panels
- 2016
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Ingår i: Journal of solar energy engineering. - : ASME International. - 0199-6231 .- 1528-8986. ; 138:4
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Tidskriftsartikel (refereegranskat)abstract
- Numerical simulation results and modeling on the electrical features of concentrating photovoltaic-thermal (PVT) using the free circuit simulation package from linear technology corporation (LTSPICE) are presented. The effects of partial shading of cell strings and temperature are analyzed, showing very good agreement with the results obtained experimentally in lab, at Lisbon University, and under outdoor testing using similar receivers, at the SME Solarus Sunpower AB, a Swedish company whose mission is the development, production, and marketing of concentrated solar technology to the world market. The potential of the used methodology for the design of the solar cell configuration is emphasized as an important tool to optimize PV and PVT performances in the energy conversion process.
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| 9. |
- Noelle, Andreas, et al.
(författare)
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UV/Vis+ photochemistry database : Structure, content and applications
- 2020
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 253
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Tidskriftsartikel (refereegranskat)abstract
- The “science-softCon UV/Vis+ Photochemistry Database” (www.photochemistry.org) is a large and comprehensive collection of EUV-VUV-UV–Vis-NIR spectral data and other photochemical information assembled from published peer-reviewed papers. The database contains photochemical data including absorption, fluorescence, photoelectron, and circular and linear dichroism spectra, as well as quantum yields and photolysis related data that are critically needed in many scientific disciplines.This manuscript gives an outline regarding the structure and content of the “science-softCon UV/Vis+ Photochemistry Database”. The accurate and reliable molecular level information provided in this database is fundamental in nature and helps in proceeding further to understand photon, electron and ion induced chemistry of molecules of interest not only in spectroscopy, astrochemistry, astrophysics, Earth and planetary sciences, environmental chemistry, plasma physics, combustion chemistry but also in applied fields such as medical diagnostics, pharmaceutical sciences, biochemistry, agriculture, and catalysis. In order to illustrate this, we illustrate the use of the UV/Vis+ Photochemistry Database in four different fields of scientific endeavor.
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| 10. |
- Shoukry, Yasser, et al.
(författare)
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SMT-Based Observer Design for Cyber-Physical Systems under Sensor Attacks
- 2016
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Ingår i: 2016 ACM/IEEE 7th International Conference on Cyber-Physical Systems, ICCPS 2016 - Proceedings. - 9781509017720
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Konferensbidrag (refereegranskat)abstract
- We introduce a scalable observer architecture to estimate the states of a discrete-time linear-time-invariant (LTI) system whose sensors can be manipulated by an attacker. Given the maximum number of attacked sensors, we build on previous results on necessary and sufficient conditions for state estimation, and propose a novel multi-modal Luenberger (MML) observer based on efficient Satisfiability Modulo Theory (SMT) solving. We present two techniques to reduce the complexity of the estimation problem. As a first strategy, instead of a bank of distinct observers, we use a family of filters sharing a single dynamical equation for the states, but different output equations, to generate estimates corresponding to different subsets of sensors. Such an architecture can reduce the memory usage of the observer from an exponential to a linear function of the number of sensors. We then develop an efficient SMT-based decision procedure that is able to reason about the estimates of the MML observer to detect at runtime which sets of sensors are attack-free, and use them to obtain a correct state estimate. We provide proofs of convergence for our algorithm and report simulation results to compare its runtime performance with alternative techniques. Our algorithm scales well for large systems (including up to 5000 sensors) for which many previously proposed algorithms are not implementable due to excessive memory and time requirements. Finally, we illustrate the effectiveness of our algorithm on the design of resilient power distribution systems.
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