In the present work blends of polystyrene (PS) with sepiolites have been produced using a melt extrusion process. The dispersion degree of the sepiolites in the PS has been analyzed by dynamic shear ...rheology and X‐ray micro‐computed tomography. Sepiolites treated with quaternary ammonium salts (O‐QASEP) are better dispersed in the PS matrix than natural sepiolites (N‐SEP) or sepiolites organo‐modified with silane groups (O‐SGSEP). A percolated network is obtained when using 6.0 wt% of O‐QASEP, 8.0 wt% of N‐SEP and 10.0 wt% of O‐SGSEP. It has been shown that multiple extrusion processes have a negative effect on the polymer architecture. They produce a reduction in the length of the polymeric chains, and they do not lead to a better dispersion of the particles in the polymer matrix. Foams have been produced using a gas dissolution foaming process, where a strong effect of the dispersion degree on the cellular structure of the different foams was found. The effects on the cellular structure obtained by using different types of sepiolites, different contents of sepiolites and different extrusion conditions have been analyzed. The foams produced with the formulations containing O‐QASEP present the lowest cell size and the most homogeneous cellular structures.
The effects of the particle's surface treatment, clay content and extrusion process in the dispersion degree of blends of PS and sepiolites were analyzed by shear dynamic rheology and X‐Ray microtomography. Cellular materials were produced, using the blends, by the gas dissolution foaming process. After the cellular structure analysis, a strong link between particle dispersion and cellular structure was found.
In this paper, the behavior of a doubly fed induction generator (DFIG) is studied under unbalanced grid voltage conditions. It is shown that if no special control efforts are employed, the behavior ...of the generator is deteriorated, basically due to two reasons: electromagnetic torque oscillations and nonsinusoidal current exchange with the grid. These phenomena are first analyzed theoretically as a function of the stator active and reactive instantaneous power exchange by the stator of the DFIG and the grid-side converter (GSC). This analysis provides the main ideas for generation of the active and reactive power references for the rotor-side converter (RSC) and the GSC, controlled by means of direct power control techniques. Therefore, this paper proposes a new algorithm that generates the RSC power references, without the necessity of a sequence component extraction, in order to eliminate torque oscillations and achieve sinusoidal stator currents exchange. On the contrary, the GSC power references are provided by means of voltage and current sequence extraction. Finally, simulation and experimental results successfully validate the proposed power reference generation methods.
•A robot-assisted laser cleaning system is developed.•The system consists of a fs pulsed laser, a 6 DOF robot and a laser profilometer.•Automatic laser processing of arbitrary objects in a full 3D ...solution is achieved.
In this work, a robot-assisted laser cleaning system is presented that allows the automatic processing of 3D objects with arbitrary geometry. The system is based on the integration of a femtosecond pulse laser with a 6-degree-of-freedom (6 DOF) robotic arm and a laser profilometer to capture the geometry of the workpiece. An automatic procedure is performed to generate cleaning paths over the geometry, which is finally targeted by a laser source by means of the prescribed robot motion; thus, both the working distance and the normal incidence of the laser beam are kept fixed for each point on the surface. The manipulator allows displacements and changes of orientation of the object to be processed following the programmed paths in a full 3D solution. The system was tested by performing the cleaning over different curved painted metal surfaces. Experimental results show the effectiveness of the proposed method that improves the efficiency of the automatic laser cleaning of 3D objects and further promotes its application to other ablation processes.
The expression and release of tissue factor is a major trigger for the activation of coagulation in patients with sepsis. Tissue factor pathway inhibitor (TFPI) forms a complex with tissue factor and ...blood protease factors leading to inhibition of thrombin generation and fibrin formation.
To determine if administration of tifacogin (recombinant TFPI) provides mortality benefit in patients with severe sepsis and elevated international normalized ratio (INR) and to assess tifacogin safety in severe sepsis, including patients with low INR.
A randomized, double-blind, placebo-controlled, multicenter, phase 3 clinical trial conducted from March 21, 2000, through September 27, 2001, in 245 hospitals in 17 countries in North America, Europe, and Israel.
The primary efficacy population consisted of 1754 patients (> or =18 years) with severe sepsis and a high INR (> or =1.2) randomly assigned to intravenous infusion of either tifacogin (0.025 mg/kg per hour for 96 hours, n = 880) or placebo (arginine citrate buffer, n = 874), and 201 patients with a low INR (<1.2) randomly assigned to receive the same dose of either tifacogin or placebo.
All-cause 28-day mortality.
Overall mortality at 28 days in the tifacogin-treated group (n = 880) vs the placebo group (n = 874) for high INR was 34.2% vs 33.9%, respectively (P =.88, Pearson chi2 test; P =.75, logistic regression model). None of the protocol-specified secondary end points differed between the tifacogin vs placebo groups. An analysis on the first 722 patients demonstrated a mortality rate of 38.9% for placebo vs 29.1% for tifacogin (P =.006, Pearson chi2 test). Tifacogin significantly attenuated prothrombin fragment 1.2 and thrombin:antithrombin complex levels (P<.001, 2-sample t test) in patients with high and low INR. Overall mortality was lower in the tifacogin response in patients with low INR (12%; n = 83) vs placebo (22.9%; n = 118) (P =.051, Pearson chi2 test; P =.03, logistic regression model). There was an increase in serious adverse events with bleeding in the tifacogin group in both cohorts (6.5% tifacogin and 4.8% placebo for high INR; 6.0% tifacogin and 3.3% placebo for low INR).
Treatment with tifacogin had no effect on all-cause mortality in patients with severe sepsis and high INR. Tifacogin administration was associated with an increase in risk of bleeding, irrespective of baseline INR.
Chile, abundant in solar and wind energy resources, presents significant potential for the production of green hydrogen, a promising renewable energy vector. However, realizing this potential ...requires an understanding of the most suitable locations for the installation of green hydrogen industries. This study proposes a quantitative methodology that identifies and ranks potential public lands for industrial use, based on a range of technical parameters (such as solar and wind availability) and socio-environmental considerations (including land use restrictions and population density). The results reveal optimal locations that can facilitate informed, sustainable decision-making for large-scale green hydrogen implementation in Chile. While this methodology does not replace project-specific technical or environmental impact studies, it provides a flexible, general classification to guide initial site selection. Notably, this approach can be applied to other regions worldwide with abundant solar and wind resources, such as Australia and Northern Africa, promoting more effective and sustainable global decision-making for green hydrogen production.
•Innovative spatial area scoring methodology for green hydrogen industrial site selection.•Novel quantitative approach for multi-criteria decision-making for Chile.•Integrating socio-environmental considerations, and technical factors in GH2 site prioritization.•Quantitative Scoring Framework for Identifying Optimal Green Hydrogen Deployment Sites.•Solar scenario shows 100 % of the GH2 industrial sites with scoring above 9.0.
•We obtain nanocellular foams by different nucleation mechanisms.•We study the micelles present on PMMA/MAM blends.•We found a clear relationship between the initial micelles and the final cells.•We ...control the nucleation process with a self-assembled nanostructuration.
Polymer foams with closed cells in the range of 90–200nm and relative densities between 0.4 and 0.6 have been produced by CO2 gas dissolution foaming from neat poly(methyl methacrylate) (PMMA) and blends of PMMA and a triblock copolymer poly(methyl methacrylate)-block poly(butyl acrylate)-block poly(methyl methacrylate), MAM. Foams produced from these PMMA/MAM blends present a clear heterogeneous nucleation mechanism showing a clear relationship between the nanostructuration of the solid blend precursors and the nucleation efficiency of block copolymers during the saturation–expansion process. This paper discusses the role of the nanostructuration pattern of PMMA/MAM blends on the cells nucleation mechanism, showing that nucleation takes place preferably on the MAM nanostructures due to a combination of their high CO2-philicity, surface tension and morphology.
•Several designs of hybrid systems are analysed in different locations of Spain.•An innovative electricity consumption profile for dwellings is presented.•The relevance of the cogeneration engine ...working hours is emphasised.•Primary energy consumption, emissions and Life Cycle Costs are calculated.•All the case studies are compared in order to determine the most optimal solutions.
The aim of this paper is to assess the performance of several designs of hybrid systems composed of solar thermal collectors, photovoltaic panels and natural gas internal combustion engines. The software TRNSYS 17 has been used to perform all the calculations and data processing, as well as an optimisation of the tank volumes through an add-in coupled with the GENOPT® software. The study is carried out by analysing the behaviour of the designed systems and the conventional case in five different locations of Spain with diverse climatic characteristics, evaluating the same building in all cases. Regulators, manufacturers and energy service engineers are the most interested in these results.
Two major contributions in this paper are the calculations of primary energy consumption and emissions and the inclusion of a Life Cycle Cost analysis. A table which shows the order of preference regarding those criteria for each considered case study is also included. This was fulfilled in the interest of comparing between the different configurations and climatic zones so as to obtain conclusions on each of them. The study also illustrates a sensibility analysis regarding energy prices. Finally, the exhaustive literature review, the novel electricity consumption profile of the building and the illustration of the influence of the cogeneration engine working hours are also valuable outputs of this paper, developed in order to address the knowledge gap and the ongoing challenges in the field of distributed generation.
In this paper, a new method for the delay compensation when using an aggregation of virtual synchronous generators is proposed. Lack of inertia in power converters can potentially provoke stability ...issues that can be mitigated by the use of virtual inertia techniques. Among those, the Virtual Synchronous Generator (VSG) concept has received strong impulse in the last years. This paper is focused on the idea of using the distributed VSG concept in a renewable power plant, in which a single Synchronous Central Angle Controller (SCAC) is used for the power control exchange at the Point of Connection (PoC), while distribution control units are employed for the local inverter control. This idea, already discussed in the literature, is in here extended to consider the implementation on industrial string-level commercial power converters, recalling the importance of accessible measurements and communication delays. In order to validate the proposal, firstly communication delays are measured and modelled. Following, simulations with different SCAC operating modes are conducted, and finally experimental results validation of different operation modes with commercial converters are presented.
This paper analyzes the dynamic behavior of the voltage control loop based on proportional-integral regulators, commonly used for grid-forming converters in 3-phase AC and DC Microgrids and ...applications that involve a DC-link voltage control. The paper proposes a simple and accurate generalized analysis useful both for the system characterization and design. Two different control schemes, based on linear (Direct Voltage Control, DVC) and quadratic voltage feedback (Quadratic Voltage Control, QVC), are analytically studied, simulated and experimentally tested, demonstrating a superior performance of the QVC under the presence of constant power loads. The operation limits, the system stability and the disturbance rejection capability are analyzed considering the effect of control and plant parameters and the effect of the different types of disturbances and the operating point, taking into account the non-linearities of the system. The analysis is mainly focused on the effect of constant power loads given their negative impact on the system performance. The study provides a generic procedure for the analysis and design of proportional-integral voltage controllers, including the selection of the system capacitance for meeting specific dynamic specifications while considering system characteristics as the load level, the stability margins and the maximum voltage deviation under disturbances.
15% of COVID-19 patients develop severe pneumonia. Non-invasive mechanical ventilation and high-flow nasal cannula can reduce the rate of endotracheal intubation in adult respiratory distress ...syndrome, although failure rate is high.
To describe the rate of endotracheal intubation, the effectiveness of treatment, complications and mortality in patients with severe respiratory failure due to COVID-19.
Prospective cohort study in a first-level hospital in Madrid. Patients with a positive polymerase chain reaction for SARS-CoV-2 and admitted to the Intermediate Respiratory Care Unit with tachypnea, use of accessory musculature or SpO2 <92% despite FiO2> 0.5 were included. Intubation rate, medical complications, and 28-day mortality were recorded. Statistical analysis through association studies, logistic and Cox regression models and survival analysis was performed.
Seventy patients were included. 37.1% required endotracheal intubation, 58.6% suffered medical complications and 24.3% died. Prone positioning was independently associated with lower need for endotracheal intubation (OR 0.05; 95% CI 0.005 to 0.54, p = 0.001). The adjusted HR for death at 28 days in the group of patients requiring endotracheal intubation was 5.4 (95% CI 1.51 to 19.5; p = 0.009).
The rate of endotracheal intubation in patients with severe respiratory failure from COVID-19 was 37.1%. Complications and mortality were lower in patients in whom endotracheal intubation could be avoided. Prone positioning could reduce the need for endotracheal intubation.
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