Hysteresis current control technique of VSI for compensation of grid-connected unbalanced loads

The global trends nowadays in the power generation industry are to supplement the electricity production using distributed generation (DG) technologies based on renewable energy resources such as photovoltaic, wind power, etc. However, failure to properly control the operation of distributed energy resources as they connect to the exiting power grid could provoke many power quality problems on the grid side. For this reason, due considerations must be given to power generation and safe running before DG units is actually integrated into the power grid. The main aim of this paper is to address the grid interconnection issues that usually arise as DG units connect to the electric grid. The proposed strategy, implemented in Matlab/Simulink environment in different operating scenarios, provides compensation for active, reactive, unbalanced, and harmonic current components of grid-connected nonlinear unbalanced loads. The simulation results obtained in this study demonstrate the level of accuracy of the proposed technique, which ensure a balance in the overall grid phase currents, injection of maximum available power from DG resources to the grid, improvement of the utility grid power factor, and a reduction in the total harmonic distortion of grid currents.     

Dual Costimulatory and Coinhibitory Targeting with a Hybrid Fusion Protein as an Immunomodulatory Therapy in Lupus Nephritis Mice Models

Systemic lupus erythematosus is a complex autoimmune disorder mostly mediated by B-cells in which costimulatory signals are involved. This immune dysregulation can cause tissue damage and inflammation of the kidney, resulting in lupus nephritis and chronic renal failure. Given the previous experience reported with CTLA4-Ig as well as recent understanding of the PD-1 pathway in this setting, our group was encouraged to evaluate, in the NZBWF1 model, a human fusion recombinant protein (Hybri) with two domains: CTLA4, blocking the CD28—CD80 costimulatory pathway, and PD-L2, exacerbating the PD-1–PD-L2 coinhibitory pathway. After achieving good results in this model, we decided to validate the therapeutic effect of Hybri in the more severe MRL/lpr model of lupus nephritis. The intraperitoneal administration of Hybri prevented the progression of proteinuria and anti-dsDNA antibodies to levels like those of cyclophosphamide and reduced the histological score, infiltration of B-cells, T-cells, and macrophages and immune deposition in both lupus-prone models. Additionally, Hybri treatment produced changes in both inflammatory-related circulating cytokines and kidney gene expression. To summarize, both in vivo studies revealed that the Hybri effect on costimulatory-coinhibitory pathways may effectively mitigate lupus nephritis, with potential for use as a maintenance therapy.     

A limit cycle approach for the parametric identification of hysteretic systems

This paper deals with the parametric identification of the Bouc–Wen model for smooth hysteresis. The interest of the problem stems from the fact that the Bouc–Wen model has been used experimentally to represent various hysteretic systems during the last few years. However, identifying the parameters of this model is not a trivial task due to the nonlinearity of the model. In the current literature, most methods devoted to the parametric identification of the Bouc–Wen model rely mainly on numerical simulations, and do not offer, to a large extent, a rigorous proof of the convergence of the estimated parameters to the true ones. This paper presents a new identification method that guarantees the exact determination of the parameters in the absence of perturbations. It is also shown that this method is robust with respect to a class of disturbances of practical interest. The applicability of this method is illustrated by means of experiments.     

Nanoscale Correlations between Metal–Insulator Transition and Resistive Switching Effect in Metallic Perovskite Oxides

Strongly correlated perovskite oxides are a class of materials with fascinating intrinsic physical functionalities due to the interplay of charge, spin, orbital ordering, and lattice degrees of freedom. Among the exotic phenomena arising from such an interplay, metal–insulator transitions (MITs) are fundamentally still not fully understood and are of large interest for novel nanoelectronics applications, such as resistive switching‐based memories and neuromorphic computing devices. In particular, rare‐earth nickelates and lanthanum strontium manganites are archetypical examples of bandwidth‐controlled and band‐filling‐controlled MIT, respectively, which are used in this work as a playground to correlate the switching characteristics of the oxides and their MIT properties by means of local probe techniques in a systematic manner. These findings suggest that an electric‐field‐induced MIT can be triggered in these strongly correlated systems upon generation of oxygen vacancies and establish that lower operational voltages and larger resistance ratios are obtained in those films where the MIT lies closer to room temperature. This work demonstrates the potential of using MITs in the next generation of nanoelectronics devices.     

Transmission Mueller matrix ellipsometry of chirality switching phenomena

Mechanisms of molecular chirality induction are fundamental to many questions in chemistry. Interest in these mechanisms is shifting toward media of increasing complexity that simultaneously exhibit linear birefringence and dichroism and where the common assumption that optical activity is the only optical effect that affects light polarization is no longer valid. Light propagation through several of these anisotropic media can be appropriately studied with transmission Mueller matrix ellipsometry. The applications presented herein include the measurement of optical activity in stirred solutions of soft-matter nanophases and the determination of chiral domains in solid-state samples.     

In-situ remediation of acid mine drainage using a permeable reactive barrier in Aznalcóllar (Sw Spain)

Following on the accident occurred in Aznalcóllar in 1998, whereby a huge amount of acid mine drainage and heavy metal-bearing pyritic sludge was released to the Agrio river valley with the subsequent contamination of groundwater, a subsurface permeable reactive barrier (PRB) was installed to mitigate the long-term impacts by the spillage. The PRB material consisted of a mixture of limestone and vegetal compost. A particular characteristic of the Agrio aquifer is its high water flow velocity (0.5-1 m/d), which may pose difficulties in its remediation using PRB technology. The present study reports the 36-month performance of the PRB. Vertical differences in water velocity were observed within the PRB, with the deeper part being slower and more effective in neutralizing pH and removing heavy metals (Zn, Al, Cu). On the other hand, partial sulfate removal appeard to be restricted to the bottom of the PRB, but with no apparent influence on downgradient water quality. The results are finally compared with the other four reported existing PRBs for AMD worldwide.     

High throughput screening of CO2 solubility in aqueous monoamine solutions

Post-combustion Carbon Capture and Storage technology (CCS) is viewed as an efficient solution to reduce CO(2) emissions of coal-fired power stations. In CCS, an aqueous amine solution is commonly used as a solvent to selectively capture CO(2) from the flue gas. However, this process generates additional costs, mostly from the reboiler heat duty required to release the carbon dioxide from the loaded solvent solution. In this work, we present thermodynamic results of CO(2) solubility in aqueous amine solutions from a 6-reactor High Throughput Screening (HTS) experimental device. This device is fully automated and designed to perform sequential injections of CO(2) within stirred-cell reactors containing the solvent solutions. The gas pressure within each reactor is monitored as a function of time, and the resulting transient pressure curves are transformed into CO(2) absorption isotherms. Solubility measurements are first performed on monoethanolamine, diethanolamine, and methyldiethanolamine aqueous solutions at T = 313.15 K. Experimental results are compared with existing data in the literature to validate the HTS device. In addition, a comprehensive thermodynamic model is used to represent CO(2) solubility variations in different classes of amine structures upon a wide range of thermodynamic conditions. This model is used to fit the experimental data and to calculate the cyclic capacity, which is a key parameter for CO(2) process design. Solubility measurements are then performed on a set of 50 monoamines and cyclic capacities are extracted using the thermodynamic model, to asses the potential of these molecules for CO(2) capture.     

The strong biocidal effect of free nitrous acid on anaerobic sewer biofilms

Several recent studies showed that nitrite dosage to wastewater results in long-lasting reduction of the sulfate-reducing and methanogenic activities of anaerobic sewer biofilms. In this study, we revealed that the quick reduction in these activities is due to the biocidal effect of free nitrous acid (FNA), the protonated form of nitrite, on biofilm microorganisms. The microbial viability was assessed after sewer biofilms being exposed to wastewater containing nitrite at concentrations of 0-120 mg-N/L under pH levels of 5-7 for 6-24 h. The viable fraction of microorganisms was found to decrease substantially from approximately 80% prior to the treatment to 5-15% after 6-24 h treatment at FNA levels above 0.2 mg-N/L. The level of the biocidal effect has a much stronger correlation with the FNA concentration, which is well described by an exponential function, than with the nitrite concentration or with the pH level, suggesting that FNA is the actual biocidal agent. An increase of the treatment from 6 to 12 and 24 h resulted in only slight decreases in microbial viability. Physical disrupted biofilm was more susceptible to FNA in comparison with intact biofilms, indicating that the biocidal effect of FNA on biofilms was somewhat reduced by mass transfer limitations. The inability to achieve 2-log killing even in the case of disrupted biofilms suggests that some microorganisms may be more resistant to FNA than others. The recovery of biofilm activities in anaerobic reactors after being exposed to FNA at 0.18 and 0.36 mg-N/L, respectively, resembled the regrowth of residual sulfate-reducing bacteria and methanogens, further confirming the biocidal effects of FNA on microorganisms in biofilms.     

Secret-Sharing Schemes for Very Dense Graphs

A secret-sharing scheme realizes a graph if every two vertices connected by an edge can reconstruct the secret while every independent set in the graph does not get any information on the secret. Similar to secret-sharing schemes for general access structures, there are gaps between the known lower bounds and upper bounds on the share size for graphs. Motivated by the question of what makes a graph “hard” for secret-sharing schemes (that is, they require large shares), we study very dense graphs, that is, graphs whose complement contains few edges. We show that if a graph with \(n\) vertices contains \(\left( {\begin{array}{c}n\\ 2\end{array}}\right) -n^{1+\beta }\) edges for some constant \(0 \le \beta <1\), then there is a scheme realizing the graph with total share size of \(\tilde{O}(n^{5/4+3\beta /4})\). This should be compared to \(O(n^2/\log (n))\), the best upper bound known for the total share size in general graphs. Thus, if a graph is “hard,” then the graph and its complement should have many edges. We generalize these results to nearly complete \(k\)-homogeneous access structures for a constant \(k\). To complement our results, we prove lower bounds on the total share size for secret-sharing schemes realizing very dense graphs, e.g., for linear secret-sharing schemes, we prove a lower bound of \(\Omega (n^{1+\beta /2})\) for a graph with \(\left( {\begin{array}{c}n\\ 2\end{array}}\right) -n^{1+\beta }\) edges.