DC-Voltage-Ratio Control Strategy for Multilevel Cascaded Converters Fed With a Single DC Source

Recently, a multilevel cascaded converter fed with a single DC source has been presented. An analysis of the steady-state working limits of this type of converter is presented in this paper. Limits of the maximum output voltage and the minimum and maximum loading conditions for stable operation of the converter are addressed. In this paper, a way to achieve any DC voltage ratio (inside the stable operation area of the converter) between the H-bridges of the single-DC-source cascaded H-bridge converter is presented. The proposed DC-voltage-ratio control is based on a time-domain modulation strategy that avoids the use of inappropriate states to achieve the DC-voltage-ratio control. The proposed technique is a feedforward-modulation technique which takes into account the actual DC voltage of each H-bridge of the converter, leading to output waveforms with low distortion. In this way, the dc voltage of the floating H-bridge can be controlled while the output voltage has low distortion independently of the desired DC voltage ratio. Experimental results from a two-cell cascaded converter are presented in order to validate the proposed DC-voltage-ratio control strategy and the introduced concepts.Ministerio de Ciencia y Tecnología TEC2006-03863Junta de Andalucía EXC/2005/TIC-117

Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio

Modulation techniques for multilevel converters can create distorted output voltages and currents if the DC link voltages are unbalanced. This situation can be avoided if the instantaneous DC voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output voltage of the power converter always generates the reference determined by the controller even in worst case voltage unbalance conditions. In addition the possibility of optimizing the DC voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5kVA prototype are presented in order to validate the proposed modulation technique

Optimization in the production of fat for the obtainment of biodiesel from sludge from treatment plants wastewater

Motivation: Most of the energy sources currently used is derived from fossil fuels, whose reserves are limited. On the other hand, millions of tonnes of waste are generated worldwide from urban water treatment. Sewerage water is treated in wastewater treatment plants (WWTP) and passed through a depuration process that generates a waste in form of sludge. In an attempt to solve those two problems we are using a strategy which involve the nematode Caenorhabditis elegans. C. elegans is a free-living nematode used as a model organism for basic biological research. Its successful as model organism for biomedical research relay in several features: it is easy to manipulate, it has a small size, a fast life cycle, a small genome and a simple anatomy. Among other traits, the ability of generating and accumulating fat and the wide range of bacteria in its diet are remarkable for this project. The general aim of this research project is to optimize the production of nematode fat useful for biodiesel, using the sludge from water depuration plant as medium to growth the nematodes. During the develop of this project, three fundamental bottlenecks have been detected: first, the sludge is not completely assimilated by the nematodes. Second, each sludge sample is diverse and generates diverse nematode production and third, In regular medium is necessary to add seven fundamental components (NaCl, KH2PO4, cholesterol, Potassium citrate, Trace Metals, CaCl2, MgSO4) to have an optimal growth of C. elegans, which is an important economical-cost.Methods: To overcome those problems, we have studied the effect of applying to the sludge a pretreatment and we are analyzing which of the components can be eliminated without affecting population growth. We also will analyze the amount of fat produced by the nematode with the Soxhlet method.Results: The following results were obtained: Microwave pretreatment increase the number of the nematode in the sludge. Addition of NaCl, KH2PO4 and Potassium citrate generates a similar nematode growth than the addition of seven components.Conclusions: We observed that it is necessary the addition of the NaCl, KH2PO4 and Potassium citrate to get an optimal growth of C.elegans in the sludge and microwave treatment generate an increase of nematode production in the sludge

In situ characterization of main reaction products in alkali-activated slag materials by Confocal Raman Microscopy

The re-use of different aluminosilicates, such as blast furnace slag, in the preparation of alternative binders (alkali-activated materials) to Portland cement materials is well document and evaluated by conventional techniques. The use of XRD, FTIR and TG techniques allows obtaining information about the hydration products formed under the conditions of alkaline activation. The formation of the main reaction product (C-A-S-H gel), due to its low crystallinity, is not easily stablished by XRD or FTIR, and it is also quite complex to obtain quantitative information. Confocal Raman Microscopy (CRM) technique reveals information of each of the present phases during the slag activation and in particular. Moreover, CRM provide the evolution of C-A-S-H gel confirming that the growth of the C-A-S-H gel in activate alkaline-systems is different from that an Ordinary Portland Cement system. C-A-S-H gel grows randomly in the regions rich in calcium and silicon. The use of CRM opens a new possibility for the in situ study of complex systems such as the activation of alkali-activated or geopolymers in the search for alternative materials to Portland cement.This work was supported by the Spanish Ministry of Economy and Competitiveness through the Project MAT-2017-86450-C4-1-R and Spanish National Research Council Project NANOMIND 201560E068. Dr. M. Torres-Carrasco is also indebted to MINECO for a postdoctoral fellowship "Juan de la Cierva-Formación" (ref: FJCI-2016-28488). In addition, O. Mikhailova enjoyed a pre-doctoral fellowship with specific junior project FAST-J-18-5568 from the Brno University of Technology (Czech Republic) for internship in Spain

Data Sources as a Driver for Market‑Oriented Tourism Organizations: a Bibliometric Perspective

This paper presents a conceptual framework that accurately represents the current and future perspectives of data-driven companies in tourism by means of an analysis of the data sources used in the data-driven tourism research literature, as well as the research topics to which they are applied. For this purpose, a bibliometric analysis of data-driven tourism research is carried out. The framework of the study is all tourism-related publications whose research was based on data sources during the period 1982–2020. The results show some of the basic bibliometric performance indicators and the maps of science. The main themes of research interest are identified, and the conceptual evolution is obtained based on these maps. Three major thematic areas are identified: tourism research topics, information sources, and data analysis techniques. Based on these three thematic areas, the conceptual model of data architecture and processes of a data-driven organization in the tourism sector are obtained. An additional qualitative analysis of the three thematic areas is performedCRUE-CSIC agreement with Springer Natur

Optimization-Based Capacitor Balancing Method with Customizable Switching Reduction for CHB Converters

This paper presents a method for switching reduction in cascaded H-bridge converters. Given the wide applicability of this topology, it would be especially desirable to increase its efficiency with switching losses reduction techniques. Since this type of converter requires voltage balancing methods, several modulation methods consider the possibility of combining the balancing and switching reduction goals together. In this paper, a previously disclosed optimization-based balance method was modified further to consider the switching losses in its objective function. Each commutation was penalized in proportion to the phase current and the module voltage, thus avoiding commutations that would produce the most losses but tolerating low-losses commutations. The structure of the original method was maintained so that the algorithm could be applied with minimal change. The results show that it is possible to reduce the switching up to 14% without any noticeable drawback and up to 22% at the cost of a greater DC-link ripple. It is also possible to selectively reduce the effective switching frequency of only some modules, making it significantly low. This extends the adaptability of the converter, possibly allowing hybrid converters with modules of different transistor technologies.Horizon 2020. Trusted European SiC Value Chain for a Greener Economy PCI2021-121986, TRANSFORM

European Registry on Helicobacter pylori Management: Effectiveness of First and Second-Line Treatment in Spain

The management of Helicobacter pylori infection has to rely on previous local effectiveness due to the geographical variability of antibiotic resistance. The aim of this study was to evaluate the effectiveness of first and second-line H. pylori treatment in Spain, where the empirical prescription is recommended. A multicentre prospective non-interventional registry of the clinical practice of European gastroenterologists concerning H. pylori infection (Hp-EuReg) was developed, including patients from 2013 until June 2019. Effectiveness was evaluated descriptively and through a multivariate analysis concerning age, gender, presence of ulcer, proton-pump inhibitor (PPI) dose, therapy duration and compliance. Overall, 53 Spanish hospitals were included, and 10,267 patients received a first-line therapy. The best results were obtained with the 10-day bismuth single-capsule therapy (95% cure rate by intention-to-treat) and with both the 14-day bismuth-clarithromycin quadruple (PPI-bismuth-clarithromycin-amoxicillin, 91%) and the 14-day non-bismuth quadruple concomitant (PPI-clarithromycin-amoxicillin-metronidazole, 92%) therapies. Second-line therapies were prescribed to 2448 patients, with most-effective therapies being the triple quinolone (PPI-amoxicillin-levofloxacin/moxifloxacin) and the bismuth-levofloxacin quadruple schemes (PPI-bismuth-levofloxacin-amoxicillin) prescribed for 14 days (92%, 89% and 90% effectiveness, respectively), and the bismuth single-capsule (10 days, 88.5%). Compliance, longer duration and higher acid inhibition were associated with higher effectiveness. “Optimized” H. pylori therapies achieve over 90% success in Spain

Studies of dust from JET with the ITER-Like Wall: Composition and internal structure

Results are presented for the dust survey performed at JET after the second experimental campaign with the ITER-Like Wall: 2013–2014. Samples were collected on adhesive stickers from several different posi- tions in the divertor both on the tiles and on the divertor carrier. Brittle dust-forming deposits on test mirrors from the inner divertor wall were also studied. Comprehensive characterization accomplished by a wide range of high-resolution microscopy techniques, including focused ion beam, has led to the iden- tification of several classes of particles: (i) beryllium flakes originating either from the Be coatings from the inner wall cladding or Be-rich mixed co-deposits resulting from material migration; (ii) beryllium droplets and splashes; (iii) tungsten and nickel-rich (from Inconel) droplets; (iv) mixed material layers with a various content of small (8–200 nm) W-Mo and Ni-based debris. A significant content of nitrogen from plasma edge cooling has been identified in all types of co-deposits. A comparison between particles collected after the first and second experimental campaign is also presented and discussed.EURATOM 63305

Evaluation of Early Cholecystectomy versus Delayed Cholecystectomy in the Treatment of Acute Cholecystitis

Objective. To evaluate if early cholecystectomy (EC) is the most appropriate treatment for acute cholecystitis compared to delayed cholecystectomy (DC). Patients and Methods. A retrospective cohort study of 1043 patients was carried out, with a group of 531 EC cases and a group of 512 DC patients. The following parameters were recorded: (1) postoperative hospital morbidity, (2) hospital mortality, (3) days of hospital stay, (4) readmissions, (5) admission to the Intensive Care Unit (ICU), (6) type of surgery, (7) operating time, and (8) reoperations. In addition, we estimated the direct cost savings of implementing an EC program. Results. The overall morbidity of the EC group (29.9%) was significantly lower than the DC group (38.7%). EC demonstrated significantly better results than DC in days of hospital stay (8.9 versus 15.8 days), readmission percentage (6.8% versus 21.9%), and percentage of ICU admission (2.3% versus 7.8%), which can result in reducing the direct costs. The patients who benefited most from an EC were those with a Charlson index > 3. Conclusions. EC is safe in patients with acute cholecystitis and could lead to a reduction in the direct costs of treatmen