| 1. |
- 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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| 2. |
- Ilanidis, Dimitrios, 1986-
(författare)
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Biochemical conversion of biomass : hydrothermal pretreatment, by-product formation, conditioning, enzymatic saccharification, and fermentability
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lignocellulosic residues have great potential as feedstocks for production of bio-based chemicals and fuels. One of the main routes is biochemical conversion, which typically includes pretreatment, enzymatic saccharification, microbial fermentation of sugars, and valorization of hydrolysis lignin. Utilization of a broad variety of lignocellulosic feedstocks and development of more efficient conversion processes are advantageous for making bio-based commodities affordable. Biochemical conversion of lignocellulosic biomass was investigated with the overall aim to understand how variations in pretreatment conditions affected yields, formation of bioconversion inhibitors, enzymatic digestibility of pretreated materials, and fermentability. Experiments included estimation of pseudo-lignin content and quantitation of recently discovered microbial inhibitors, such as formaldehyde and p-benzoquinone. Conditioning of pretreated material to improve the efficiency of reactions with biocatalysts was further investigated.Hydrothermal pretreatment of sugarcane bagasse was investigated by using both autocatalyzed and sulfuric-acid-catalyzed pretreatment and by varying temperature and time in such a way that the severity factor was maintained at one of three predetermined values. For autocatalyzed pretreatments, the enzymatic digestibility of the pretreated solids was directly proportional to the severity. Pretreatment conditions that were just harsh enough to almost quantitatively solubilize hemicelluloses gave the best results. Potential effects of the redox environment during hydrothermal pretreatment were investigated by addition of oxygen gas or nitrogen gas in experiments with sugarcane bagasse and Norway spruce. The investigation demonstrated that gas addition, and especially addition of oxygen gas, can be used to modulate the severity of acidic hydrothermal pretreatment. Hydrothermal pretreatment of wheat straw was investigated to evaluate the impact of pretreatment conditions on newly discovered inhibitors, enzymatic digestibility, and fermentation. An increase of the temperature up to 190 °C in autocatalyzed pretreatment led to high combined glucose and xylose yields; up to ~480 kg/ton (dry weight) raw wheat straw. A correlation between enzymatic digestibility and removal of hemicelluloses was observed. A techno-economical evaluation of several conditioning methods for slurries of steam-pretreated spruce indicated that treatment with sodium sulfite was the most favorable option. Treatments with sulfite and dithionite successfully decreased the concentration of formaldehyde. Results also indicate that increased temperature in conditioning of hydrolysate could to some extent compensate for using lower dosages of sodium dithionite.
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| 3. |
- Souza, Lamartine, et al.
(författare)
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Impact of Non-Stationary Noise on xDSL Systems: an Experimental Analysis
- 2007
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. ; 6603
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Konferensbidrag (refereegranskat)abstract
- Broadband services require data rates that can only be achieved by using relatively high spectrum frequencies. At such high frequencies, the DSL (Digital Subscriber Line) signal is more susceptible to external noise sources, such as radio frequency interference and impulsive noise. This paper aims to characterize how the impulsive noise impacts on services and applications for a broadband system using an ADSL2+ loop. The first approach was to use the impulsive noise defined in the standards G.996.1 (Test Procedures for DSL Transceivers) from ITU-T and TR-048 (ADSL Interoperability Test Plan) from DSL Forum. In this approach we have also used a HDSL (High Bit Rate DSL) and white noise disturbers on the line. The impulsive noises c1 and c2 (defined in G.996.1) are injected into the circuit at the CO (Central Office) end and CPE (Customer Premises Equipment) end of the loop simulator. Additionally, it was analyzed the spikes of noise's impact on the ADSL2+ line. In this case, pre-defined models of NEXT (Near-end crosstalk) and white noise are injected on CO and CPE side, simultaneously. Metrics like packet rate, lost packet count, bandwidth, short-term average transfer delay, and errored seconds are used to characterize the DSL loop under the noise impairments.
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| 4. |
- Castro, Eulogio, et al.
(författare)
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Pretreatment and bioconversion for valorization of residues of non-edible oilseeds
- 2023
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Ingår i: Agronomy. - : MDPI. - 2073-4395. ; 13:9
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Forskningsöversikt (refereegranskat)abstract
- Biodiesel production currently follows a first-generation model using edible oils as raw materials. Such a production model is unsustainable, considering that it is limited by the high cost of edible oils, competes with the food sector, and is linked to deforestation and other environmental threats. Changing the raw material base to non-edible oils provides an opportunity to increase the sustainability of the biodiesel industry and to avoid conflicts with food production. Processing non-edible oilseeds for extracting the oil to be used for producing biodiesel generates large amounts of residues, such as de-oiled cakes, seed husks, and fruit shells and pods as well as plant stems and leaves resulting from pruning and other agronomy practices. Most of those residues are currently disposed of by burning or used in a suboptimal way. Bioconversion following the sugar platform route, anaerobic digestion, or enzyme production provides means for upgrading them to advanced biofuels and high-added value products. Bioconversion of plant biomass, including oilseed residues, requires pretreatment to enhance their susceptibility to enzymes and microorganisms. This review provides an outlook on bioconversion approaches applicable to different residues of oilseed-bearing plant species. Recent reports on the pretreatment of non-edible oilseed residues for enhancing their bioconversion through either the sugar platform route or anaerobic digestion are critically discussed. This review is based on an exhaustive Web of Science search performed in January–May 2023.
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| 5. |
- Hernández-Laguna, Alfonso, et al.
(författare)
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Compressibility of 2M1 muscovite-phlogopite series minerals
- 2019
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Ingår i: Journal of Molecular Modeling. - : Springer. - 1610-2940 .- 0948-5023. ; 25:11
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Tidskriftsartikel (refereegranskat)abstract
- Muscovite (Ms) and phlogopite (Phl) belong to the 2:1 dioctahedral and trioctahedral layer silicates, respectively, and are the end members of Ms-Phl series minerals. This series was studied in the 2M1 polytype and modeled by the substitution of three Mg2+ cations in the Phl octahedral sites by two Al3+ and one vacancy, increasing the substitution up to reach the Ms. The series was computationally examined at DFT level as a function of pressure to 9 GPa. Cell parameters as a function of pressure and composition, and bulk moduli as a function of the composition agrees with the existing experimental results. The mixing Gibbs free energy was calculated as a function of composition. From these data, approximated solvi were calculated at increasing pressure. A gap of solubility is found, decreasing the gap of solubility at high pressure.
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| 6. |
- Jones, Geraint H., et al.
(författare)
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The Comet Interceptor Mission
- 2024
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Ingår i: Space Science Reviews. - : Springer Nature. - 0038-6308 .- 1572-9672. ; 220:1
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Tidskriftsartikel (refereegranskat)abstract
- Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum Δ V capability of 600 ms − 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.
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| 7. |
- Martinez-Osuna, Juan F., et al.
(författare)
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Coastal buoy data acquisition and telemetry system for monitoring oceanographic and meteorological variables in the Gulf of Mexico
- 2021
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Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a data acquisition and telemetry system designed and built to monitor oceanographic and meteorological parameters. A voltage regulator and readout module was designed for the reading of data from a set of dedicated commercial sensors and to continuously monitor the voltage level of the power supply. In order to monitor the measured parameters and the status of the buoy remotely, a data string was transmitted every hour using an Iridium satellite transceiver. The described system was implemented and tested in four coastal oceanographic buoys that were deployed and operated in remote sites in the Gulf of Mexico (GoM) for several months in 2016. The data recorded by the buoys is used to describe the oceanographic and meteorological conditions at each site. The system proved to be reliable for long-term monitoring at offshore sites, requiring only minor corrective maintenance during their operation in the field.
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| 8. |
- Ugalde Loo, Carlos Ernesto, et al.
(författare)
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Individual Channel Analysis of the Thyristor-Controlled Series Compensator Performance
- 2010
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Ingår i: International Journal of Emerging Electric Power Systems. - 2194-5756 .- 1553-779X. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- The TCSC is the electronically-controlled counterpart of the conventional series bank of capacitors. A mature member of the FACTS technology, the TCSC has the ability to regulate power flows along the compensated line and to rapidly modulate its effective impedance. In this paper its performance is evaluated using Individual Channel Analysis and Design. Fundamental analysis is carried out to explain the generator dynamic behavior as affected by the TCSC. Moreover, a control system design for the system is presented, with particular emphasis in the closed-loop performance and stability and structural robustness assessment. It is formally shown that the incorporation of a TCSC operating in its capacitive range improves the dynamical performance of the synchronous machine by decreasing the electrical distance and therefore considerably reducing the awkward switchback characteristic exhibited by synchronous generators. It is also formally proven in the paper that the inductive operation should be avoided as it impairs system operation. In general, the TCSC inclusion brings on fragility into the global system, making it non-minimum phase and introducing adverse dynamics in the speed channel of the synchronous machine. Moreover, it is shown that the minimum-phase condition may also be present in cases featuring high capacitive compensation levels.
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| 9. |
- Ugalde Loo, Carlos Ernesto, et al.
(författare)
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Synchronous Generators Modeling and Control Using the Framework of Individual Channel Analysis and Design : Part 1
- 2007
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Ingår i: International Journal of Emerging Electric Power Systems. - : Berkeley Electronic Press. - 2194-5756 .- 1553-779X. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a comprehensive dynamical assessment of a high order synchronous generator plant is carried out using the Individual Channel Analysis and Design (ICAD) framework – a multivariable control engineering tool that allows robustness and system performance evaluations. The great benefits of ICAD are elucidated and contrasted to those provided by the long-time honored block diagram representations. Several models used for the small signal stability analysis of synchronous generators are evaluated under the framework of ICAD. The study, which builds on pioneering work, reveals the great advantages of carrying out control system analysis and design with higher order generator models. Moreover, careful analysis of the ICAD’s Multivariable Structure Function (MSF) helps to explain, formally, why some operating conditions of the control system are more critical than others. Furthermore, correct interpretations of MSFs are amenable to robust and stable control system designs. Two kinds of studies are considered in the paper; one assesses operation under various power factor conditions and the other under a varying tie-line reactance. The control system design and stability and structural robustness assessment of the system are presented in the second part of this paper. Moreover, results obtained under the ICAD framework are compared with those arising from conventional controllers.
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| 10. |
- Vanfretti, Luigi, et al.
(författare)
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Fundamental Analysis of the Synchronous Generator : TCSC System using the ICAD Framework
- 2008
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Konferensbidrag (refereegranskat)abstract
- The TCSC, a mature member of the FACTS technology, is the electronically-controlled counterpart of the conventional series bank of capacitors. Its major bene-fits are its ability to regulate power flows along the com-pensated line and to rapidly modulate its effective imped-ance. In this paper, fundamental analysis of the synchro-nous generator – TCSC system using Individual Channel Analysis and Design, is carried out. The main benefits of this approach in control system design tasks are elucidated. Fundamental analysis is used to explain the generator dynamic behaviour as affected by the TCSC. The system is modelled as a 3x3 multivariable plant. Moreover, a control system design for the system is presented, with particular emphasis in the closed-loop performance and stability and structural robustness assessment. The percentage of series compensation is varied (50, 25 and 10%) by changing the firing angle of the TCSC. It is formally shown that the addition of the TCSC improves the dynamical performance of the synchronous machine by substantially decreasing the electrical distance and therefore considerably reducing the awkward switch-back characteristic exhibited by synchro-nous generators. However, the TCSC inclusion brings on fragility to the global system, making it non-minimum phase and introducing adverse dynamics in the speed channel of the synchronous machine.
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