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The enzymatic oxidation process that causes black spots on shrimp, named melanosis, leads to spoilage and economic losses. Therefore, there is an urgent need for strategies to reduce melan...

Power systems have incorporated many new technologies in recent years and the introduction of energy storage systems and demand response provides additional challenges for their operation and expansion planning. Current distribution networks are complex active networks where many technologies are included, which must be considered and properly represented in expansion planning models. Thus, this paper proposes a robust model to solve the coordinated operation and expansion planning of active distribution networks with multiple microgrids, distributed energy resources (DERs), demand response, and N-1 generation contingency. The objective is to determine the best expansion planning proposals and the optimal daily operation (24-hour representation) for the DERs under the worst realization of uncertainties, using a contingency-constrained approach. Besides, the load is represented by non-controllable, controllable, and deferrable portions. The model is formulated as a tri-level problem that is solved using a two-stage robust optimization approach. The proposed method is illustrated using a modified version of the IEEE 123-bus test system. The results show that the coordinated operation and expansion planning decreases the total cost of the problem and provides more consistent results for demand response and DERs coordination. Simulations show a reduction of 13.8% in the total cost if the daily operation and demand response are represented, and the inclusion of contingencies provides a reduction of 70% in the EENS (expected energy not served) reliability index for the case study.

In this study, we analyzed seed wettability as well as imbibition and germination after treatment with atmospheric pressure cold plasma (APCP) using dielectric barrier discharge (DBD) in seeds that have very low germination rates. To aid industrial applications, several seeds were simultaneously treated with plasma within a space between two coaxial glass tubes sandwiched by two metal mesh screens that produced high-voltage pulses at 17.5 kV with a frequency of 990 Hz. Three treatment times (3 min, 9 min and 15 min) as well as untreated seeds were used to conduct the wettability, imbibition and germination tests. The wettability and imbibition were found to be directly related to the treatment duration, but saturation of the imbibition was found for treatment durations greater than 9 min. Plasma treatment was also effective in improving germination, but shorter treatment duration presented greater germination. This apparent contradiction is explained by the cell damage caused by the increased exposure to plasma, as observed in other studies. The results suggest that there must be an optimal wettability and imbibition condition that ensures that excessive moisture does not harm the germination process.

Biomedical devices introduced in the human body interact initially with blood cells, their success being dependent on the result of this interaction. This work aimed to obtain optimum biocompatibility and hemocompatibility of the titanium by plasma treatment. For this, discs of commercially pure titanium (CP) were subjected to plasma nitriding using different mixture of nitrogen and hydrogen; the effect of addition of hydrogen to the nitriding plasma was investigated. Before and after treatment, samples were evaluated in terms of topography and wettability using atomic force microscopy and sessile drop tests, respectively. The titanium biological response was evaluated in vitro through the application of platelet-rich plasma (PRP) on the surfaces modified and analysis of their behaviour from the point of view of surface tension and cell adhesion. Surface properties, such as roughness and wettability, were sensitive to the hydrogen/nitrogen ratio in the nitriding plasma, suggesting a strategy for producing different surfaces of biomedical devices. Results showed to be possible to obtain surfaces with different response to the adhesion of platelets, covering different applications.

In the present work, Al2O3/ZrO2 nanocomposite surfaces were treated with cold plasma using N 2 , H 2 , and O 2 gaseous atmospheres. For this, Al2O3/ZrO2 samples were shaped and sintered at 1500 °C for 2 h. Then, the surfaces were treated with cold plasma using different N 2 and O 2 gas flow proportions. The H 2 gas flow was maintained at 50%. The treatment conditions were a total gas flow rate of 20 sccm, total pressure of 2.0 mbar, square pulses of voltage with duration of the 50 µs repeated every 100 µs, and a temperature of 400 °C. The surface treatment, regardless of the gaseous atmospheres, affected the functional groups attributed to ZrO2 significantly more than those of Al2O3. In general, it was observed that the surfaces treated in gaseous atmospheres with a higher proportion of N 2 gas flow had a more hydrophilic character due to the greater amount of active species coming from this gas. Although active N 2 gas species are predominant, active O 2 gas species can also affect ZrO2 functional groups. Thus, the pre-treatment contributes both to increasing hydrophilic character as well as promoting chemical changes in the functional groups present on the nanocomposite surfaces.

We evaluated the effects of titanium plasma nitriding and oxidation on live endothelial cell viscoelasticity. For this, mechanically polished titanium surfaces and two surfaces treated by planar cathode discharge in nitriding (36N2 and 24H2) and oxidant (36O2 and 24H2). Surfaces were characterized regarding wettability, roughness and chemical composition. Rabbit aortic endothelial cells (RAECs) were cultured on the titanium surfaces. Cell morphology, viability and viscoelasticity were evaluated by scanning electron microscopy (SEM), methyl thiazolyl tetrazolium (MTT) assay and atomic force microscopy (AFM), respectively. Grazing Incidence X-ray Diffraction confirmed the presence of TiN0,26 on the surface (grazing angle theta 1°) of the nitrided samples, decreasing with depth. On the oxidized surface had the formation of TiO3 on the material surface (Theta 1°) and in the deeper layers was noted, with a marked presence of Ti (Theta 3°). Both plasma treatments increased surface roughness and they are hydrophilic (angle < 90°). However, oxidation led to a more hydrophilic titanium surface (66.59° ± 3.65 vs. 76.88° ± 2.68; p = 0.001) due to titanium oxide films in their stoichiometric varieties (Ti3O, TiO2, Ti6O), especially Ti3O. Despite focal adhesion on the surfaces, viability was different after 24 h, as cell viability on the oxidized surface was higher than on the nitrided surface (9.1 × 103 vs. 4.5 × 103cells; p < 0.05). This can be explained by analyzing the viscoelastic property of the cellular cytoskeleton (nuclear and peripheral) by AFM. Surface oxidation significantly increased RAECs viscoelasticity at cell periphery, in comparison to the nucleus (2.36 ± 0.3 vs. 1.5 ± 0.4; p < 0.05), and to the RAECs periphery in contact with nitrided surfaces (1.36 ± 0.7; p < 0.05) and polished surfaces (1.55 ± 0.6; p < 0.05). Taken together, our results have shown that titanium plasma treatment directly increased cell viscoelasticity via surface oxidation, and this mechanobiological property subsequently increased biocompatibility.

We provide new evidence on how monetary policy affects investment and firm finance in the United States and the United Kingdom. Younger firms paying no dividends exhibit the largest and most significant change in capital expenditure – even after conditioning on size, asset growth, Tobin’s Q, leverage or liquidity – and drive the response of aggregate investment. Older companies, in contrast, hardly react at all. After a monetary policy tightening, net worth falls considerably for all firms but borrowing declines only for younger non-dividend payers, as their external finance is mostly exposed to asset value fluctuations. Conversely, cash-flows change less markedly and more homogeneously across groups. Our findings highlight the role of firm finance and financial frictions in amplifying the effects of monetary policy on investment.

Supermartensitic stainless steels (SMSS) are commonly employed in the oil exploitation industry and present a good balance between the necessary physical and chemical properties and financial costs. Certain applications, such as in extreme corrosive and abrasive environments, demand improvements in the surface properties of these steels. In the present work, HP13Cr SMSS with a fully martensitic microstructure were plasma nitrided in the 350–450 °C range. The high diffusivity and low solubility of nitrogen in the martensitic structure allowed the production of thick layers (16–61 μm) containing ɛ-Fe2–3N, γ′-Fe4N and expanded phase (αN) in all the temperatures. In addition, anisotropic sputtering rate and N-diffusion were observed for different grain orientations. Mechanical properties were measured by instrumented indentation, appropriately corrected from roughness effects on the results. Hardness profiles increased from 3.8 GPa (bulk) to ∼14 GPa (near surface region) in all the working temperatures, whereas the elastic modulus was 230 GPa, presenting no statistically significant differences with respect to the bulk value. Nanoscratch tests revealed a hardened-ductile like behavior of these nitride layers. The surface tribo-mechanical behavior was correlated with elastic–plastic responses of the precipitate-containing texturized layers. Results are interpreted in light of the effectiveness of plasma nitriding to modify the surface properties of SMSS.

The mechanical and tribological properties of martensitic AISI 420 (MSS) and supermartensitic HP13Cr (SMSS) stainless steels plasma nitrided using the cathodic cage design were investigated. Nitride compounds were produced in the plasma from the cage´s sputtered ions, which eventually deposited on the electrically isolated sample. Prior to nitriding, samples were austenitized and oil quenched in order to attain a fully martensitc microstructure. Nitriding was carried out at different temperatures (350-450 °C) for 6 h. Mechanical properties and scratch resistance were characterized by instrumented indentation and nanoscratch, and were correlated with morphological and microstructural changes by using atomic force microscopy, scanning electron microscopy, X-ray diffraction and profilometry. Both nitrided MSS and SMSS comprised two distinct regions: (i) an outermost nitride layer (300-800 nm thick) containing deposited e-Fe 2 -3 N and γ´-Fe 4 N nitrides and (ii) a diffusion zone composed of N-expanded martensite phase α N . At 450 °C, diffusion zones thicknesses were 4 μm (MSS) and 6 μm (SMSS). Nitride layers presented intense brittleness under normal and tangential loadings. Critical loads for nitride layer detachment were 49 mN and 127 mN for MSS and SMSS, respectively. However, after removal of the thin nitride layers, the toughened diffusion zones were revealed, being uniformly distributed through the entire sample area. Its hardness was 11 GPa. Such value corresponds to a twofold and threefold increase from the hardness of MSS and SMSS substrates, respectively, which are comparable with other plasma nitrided steels at similar temperature conditions.

In this study, we assess how the ratio (N2/H2) – working atmosphere gas mixture – influences the properties of the layers produced on austenitic stainless steel surface by Cathodic Cage Plasma Nitriding (CCPN). The nitriding atmospheres contained nitrogen and hydrogen in three proportions: 20% N2 + 80% H2, 50% N2 + 50% H2, and 80% N2 + 20% H2 delivered at a flow rate of 20 sccm. The effect of 100% N2 was also examined. The morphology, microstructure and electrochemical properties of the layer produced were studied. The samples characteristics were determined by optical microscopy, x-ray diffraction, microhardness test and electrochemical potential curves.

A novel multiobjective, multiarea and multistage model to long-term expansion planning of integrated generation and transmission corridors incorporating sustainable energy developing is presented in this paper. The proposed MESEDES model is a “bottom-up” energy model which considers the electricity generation/transmission value-chain, i.e., power generation alternatives including renewables, nuclear and traditional thermal generation along with transmission corridors. The model decides the optimal location and timing of the electricity generation/transmission abroad the multistage planning horizon. The proposed model considers three objectives belonging to sustainable energy development criteria such as: (a) the minimization of investments and operation costs of power generation, transmission corridors, energy efficiency (demand side management (DSM) programs) considering CO2 capture technologies; (b) minimization of Life-Cycle Greenhouse Gas Emissions (GHG); and (c) maximization of the diversification of electricity generation mix. The proposed model consider aspects of the carbon abatement policy under the CDM – Clean Development Mechanism or European Union Greenhouse Gas Emission Trading Scheme. A case study is used to illustrate the proposed framework.

This paper proposes a new hybrid approach based on nonlinear chaotic dynamics and evolutionary strategy to forecast electricity loads and prices. The main idea is to develop a new training or identification stage in a nonlinear chaotic dynamic based predictor. In the training stage five optimal parameters for a chaotic based predictor are searched through an optimization model based on evolutionary strategy. The objective function of the optimization model is the mismatch minimization between the multistep-ahead forecasting of predictor and observed data such as it is done in identification problems. The first contribution of this paper is that the proposed approach is capable of capturing the complex dynamic of demand and price time series considered resulting in a more accuracy forecasting. The second contribution is that the proposed approach run on-line manner, i.e. the optimal set of parameters and prediction is executed automatically which can be used to prediction in real-time, it is an advantage in comparison with other models, where the choice of their input parameters are carried out off-line, following qualitative/experience-based recipes. A case study of load and price forecasting is presented using data from New England, Alberta, and Spain. A comparison with other methods such as autoregressive integrated moving average (ARIMA) and artificial neural network (ANN) is shown. The results show that the proposed approach provides a more accurate and effective forecasting than ARIMA and ANN methods.

Titanium (Ti) is currently the most widely used material for the manufacture of orthopedic and dental implants. Changes in the surface of commercial pure Ti (cp Ti) can determine the functional response of cells, and is therefore a critical factor for the success of the implant. However, the genotoxicity of titanium surfaces has been poorly studied. Thus, the purpose of this study was to evaluate the genotoxic potential of a new titanium surface developed by plasma treatment using argon-ion bombardment and compare it with an untreated titanium surface. Accordingly, comet assay, analysis of chromosomal aberrations (CAs), and Cytokinesis Block Micronucleus (CBMN) assay were carried out, using CHO-K1 (Chinese hamster ovary) cells grown on both titanium surfaces. Our results show that the untreated titanium surface caused a significant increase in % tail moment, in the number of cells with CAs, tetraploidy, micronucleus frequency, and other nuclear alterations when compared with the negative control and with the plasma-treated titanium surface. This difference may be attributed to increased surface roughness and changes in titanium oxide layer thickness.

Cathodic cage plasma nitriding is a new growth technique based on multiple hollow cathode effects. The samples are kept at a floating potential inside a cage that acts as a cathode and shields the samples from the cathodic potential. The aim of this work is to perform a systematic study of the properties of nitrided layers as a function of the distance from the nitriding sample surface to the cage wall using this technique. Cylindrical austenitic stainless steel AISI 316 samples were placed in different positions on an alumina plate inside the cathodic cage. The nitrided samples were characterized by optical microscopy, X-ray diffraction and microhardness measurements. The results show that the temperature inside the cage is nearly uniform and that the nitrided layers possess good physical properties and uniformity. Therefore, the differences in the nitrided layer thicknesses obtained at different positions must be due to particle flow reaching the sample surface, depending on how far the sample is from the cage walls.

Tantalum is a very interesting metal for industry due to some properties such as high melting point, ductility, high corrosion resistance, besides attractive electric and thermal conductivities. In the present work, the production of metallic tantalum (Ta) has been investigated through the reduction of Ta2O5 by aluminothermic reduction technique (ATR), using hydrogen plasma to trigger the exothermal reaction. Ta2O5 and Al mixtures were previously processed by mechanical alloying during 2, 6 and 10 h. The results obtained by XRD and SEM show that is possible to obtain a compound rich in tantalum through the technique of aluminothermic reduction by plasma.

A novel technique of aluminothermic reduction of tantalum oxide is developed to produce tantalum in form of powder. In this technique, hydrogen plasma is used to trigger the reaction in a plasma reactor. The reacted powders were analyzed by XRD and SEM. Rietveld method was used to quantify the phases present in the product of reaction. The results showed that a tantalum rich phase with a dendritic structure, typical of molten phases is formed. This phase occurred in significant amounts onto the surface and in bulk of the reacted grains.

Structural, mechanical and tribological properties of AISI 304 steel submitted to nitrogen glow discharge at different atmospheres (N 2 :H 2 , 60:40) and (N 2 :H 2 , 20:80) and substrate temperatures are reported. Expanded austenite γ N and Fe–Cr nitrides were identified as a function of the working conditions. Rietveld refinements indicate that ɛ-Fe 2+ x N is the predominant phase for the poorest nitrogen atmosphere while γ′-Fe 4 N phase is major for the richest one. The nitriding produces a surface hardening that can reach hardness values up to 14 GPa. Thicker nitrided regions are obtained in high nitriding temperatures. Reciprocating sliding tests in samples with rich or poor nitrogen atmosphere indicated long running-in regimes for high nitriding temperature. Both nitrogen atmospheres reduced the wear up to a factor of six even at the lowest temperature process. The nanoscratch tests do not show difference in the surface elastic recovering in all used nitriding conditions.

Samples of austenitic stainless steel AISI 316 were nitrided using the cathodic cage technique with the addition of methane in the nitriding atmosphere. The aim was to study the influence of this technique in reducing the precipitation of chromium nitrite and in improving the wear resistance. The results show that there was a significant improvement in such properties when compared to the results of ionic plasma nitriding. Formation of a double layer, one more internal composed of carbon and another with high nitrogen content, was confirmed by Scanning Electron Microscopy (SEM). The microhardness profile of the layer showed an increase in hardness values and a larger uniformity, while X-ray analysis showed less chromium nitriding precipitation when compared with results obtained for samples treated using ionic plasma nitriding.

The sintering under plasma heating of a powder mixture Ta–20w%Cu prepared by high energy milling is focused. The powder has composite particles in which Ta and Cu phases are amorphous. Plasma is able to heat the samples at a very high rate, but large temperature gradients are produced. The sintering of the Ta–Cu composite powder starts before Cu melting. Cu leaves the composite particles, forming a layer. This layer creates necks between the composite particles. Above the copper melting point, liquid copper leaves the composite particles and fills the pores. The composite particles rearrange but keep their original shape and size. Disintegration of composite particles is not observed due to the short sintering time used in the work. The final sintered structure is heterogeneous.

Nowadays, in plastic industry, mills are used to recycle residues generated from the manufacture of plastic components. These mills contain cut blades that suffer accelerated wear, since they are continually submitted to tribological efforts. This fact reduces its useful life. In this work, a new technique of plasma nitriding, called “cathodic cage”, was investigated. This technique eliminates some problems, like restriction rings, inherent of the conventional plasma nitriding. It was used AISI 4340 steel in substitution to AISI 01 steel, normally used in the cut blades manufacture. The AISI 4340 steel was, then, nitrided by conventional and cathodic cage techniques. After this stage, commercial and nitrided cut blades were submitted to analysis of acting. The AISI 4340 steel nitrided by cathodic cage presented uniforms thickness and hardness in the nitrided layer, promoting the average increase of 58% in its useful life, when compared with commercial blades.

In response to an interest rate change, mortgagors in the United Kingdom and United States adjust their spending significantly (especially on durable goods) but outright home-owners do not. While the dollar change in mortgage payments is nearly three times larger in the United Kingdom than in the United States, these magnitudes are much smaller than the overall change in expenditure. In contrast, the income change is sizable and similar across both household groups and countries. Consistent with the predictions of a simple heterogeneous agents model with credit-constrained households and multi-period fixed-rate debt contracts, our evidence suggests that the general equilibrium effect of monetary policy on income is quantitatively more important than the direct effect on cash flows.