In the last few decades, several papers were published on heat exchanger network synthesis. Most of them present techniques using mathematical programming for the synthesis and optimisation tasks. ...Recent developments in heat exchanger networks synthesis present some heurist methods, such as genetic algorithm (GA) and simulated annealing. In this paper, a strategy for the synthesis and optimisation of heat exchanger networks was developed using GA. First of all, the Δ
T
min is optimised using GA jointly with the problem table, from the Pinch Analysis. By using the optimum Δ
T
min, found in the previous stage, the problem is divided in two different regions, below and above the pinch. Thus, using GA, the optimal networks above and below the pinch are obtained, considering stream splitting as well. Some examples from the literature were solved with the proposed systematic, and results show heat exchanger networks with lower costs than those ones presented in the literature for the cases studied.
Aircraft soot has a significant impact on global and local air pollution and is of particular concern for the population working at airports and living nearby. The morphology and chemistry of soot ...are related to its reactivity and depend mainly on engine operating conditions and fuel-type. We investigated the morphology (by transmission electron microscopy) and chemistry (by X-ray micro-spectroscopy) of soot from the exhaust of a CFM 56-7B26 turbofan engine, currently the most common engine in aviation fleet, operated in the test cell of SR Technics, Zurich airport. Standard kerosene (Jet A-1) and a biofuel blend (Jet A-1 with 32% HEFA) were used at ground idle and climb-out engine thrust, as these conditions highly influence air quality at airport areas. The results indicate that soot reactivity decreases from ground idle to climb-out conditions for both fuel types. Nearly one third of the primary soot particles generated by the blended fuel at climb-out engine thrust bear an outer amorphous shell implying higher reactivity. This characteristic referring to soot reactivity needs to be taken into account when evaluating the advantage of HEFA blending at high engine thrust. The soot type that is most prone to react with its surrounding is generated by Jet A-1 fuel at ground idle. Biofuel blending slightly lowers soot reactivity at ground idle but does the opposite at climb-out conditions. As far as soot reactivity is concerned, biofuels can prove beneficial for airports where ground idle is a common situation; the benefit of biofuels for climb-out conditions is uncertain.
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•Soot produced by conventional kerosene Jet A-1 at ground idle is most prone for reaction.•Biofuel leads to soot reactivity reduction at ground idle but not at climb-out conditions.•Soot reactivity decreases with increasing engine thrust.•Considering soot reactivity, biofuel may prove beneficial for ground idle; the benefit for climb-out is uncertain.
Conventional kerosene (Jet A-1) at ground idle produces the most reactive soot; biofuel can prove beneficial for ground idle; its advantage for climb-out is uncertain.
In this paper, we develop a method based on local maximum entropy shape functions together with enrichment functions used in partition of unity methods to discretize problems in linear elastic ...fracture mechanics. We obtain improved accuracy relative to the standard extended finite element method at a comparable computational cost. In addition, we keep the advantages of the LME shape functions, such as smoothness and non-negativity. We show numerically that optimal convergence (same as in FEM) for energy norm and stress intensity factors can be obtained through the use of geometric (fixed area) enrichment with no special treatment of the nodes near the crack such as blending or shifting.
•The phenolic composition of 25 varieties of roselle (Hs) was determined.•A total of 7 new compounds were tentatively characterized in Hs extracts.•The Hs extracts exhibited potent antioxidant and ...antimicrobial activities.•Roselle varieties were classified based on their anthocyanin content.
This study reports the phytochemical profile (phenolics, flavonoids and anthocyanins), the antioxidant capacity and the antibacterial activity of the ethanolic extracts of a collection of 25 Mexican Hibiscus sabdariffa (Hs) varieties with different calyx color intensities, from green–yellow to deep red, cultivated in the same condition. A great variety of phenolic compounds were identified in the different extracts using HPLC-DAD-ESI-TOF-MS, mainly phenolic acids, flavonoids, and anthocyanidin, some of which have been described for the first time. The total phenolic, flavonoid and anthocyanidin contents showed great variation in the different Hs extracts, ranging from 2400±300 to 10,000±400mg gallic acid equivalents (GAE)/100g dry calyx (dc), from 419±2 to 2260±70mg quercetin/100g dc, and from 0 to 4408mg/100g dc with different ratios of delphinidin:cyanidin, respectively. Furthermore, the antioxidant capacity determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay presented the same behavior, with values that varied from 27.4±0.3 to 112±8mol equivalent trolox/g dc. In addition, the antibacterial activity of the HS extracts was assayed against Gram-negative (Escherichia coli, Salmonella enteritidis) and Gram-positive (Staphylococcus aureus, Micrococcus luteus) microorganisms, demonstrating that the ethanol extracts were effective against all the bacterial strains tested, showing a greater effect against Gram-positive bacteria. Finally, a multivariate analysis for the classification of the Hs varieties has been carried out based on the anthocyanidin content. The results reported in this paper shows for the first time antibacterial and phytochemistry diversity of the different varieties of Hs, which highlights the importance of a correct description of Hs materials used in research papers.
Layered MgMoN
2
was prepared by solid state reaction at high temperature between Mo and Mg
3
N
2
in N
2
which represents a simple synthetic pathway compared to the previously reported method that ...used NaN
3
as the nitrogen source. The crystal structure of MgMoN
2
was studied by synchrotron X-ray and neutron powder diffraction. The feasibility of oxidizing this compound and concomitantly extracting magnesium from the structure was assessed by both chemical and electrochemical approaches, using different protocols. The X-ray diffraction patterns of the oxidized samples do not exhibit any relevant difference with respect to that of the as prepared MgMoN
2
and no differences in the cell parameters are deduced from Rietveld refinements. No hints pointing at the presence of any amorphous phase are observed either. These results are rationalized through DFT calculated energy barriers for Mg
2+
ion migration in MgMoN
2
.
Extraction of magnesium from MgMoN
2
was attempted by different methods but the migration barriers were found to be too high.
In natural gas sweetening processes, expensive technologies are usually applied, where adsorption can be a viable and economic alternative. In this sense, the usage of adsorption for natural gas ...sweetening depends on adsorbent potentiality. Thus, in this work, the potential usage of FAU NaX and NaY for natural gas sweetening at high-pressure (4 MPa) and ambient temperature (298 K) by adsorption processes was investigated by simulations using a validated Multicomponent Potential Theory of Adsorption coupled to Dubinin–Radushkevitch–Astakhov model (MPTA-DRA). Pure component adsorption data for H
2
S, CO
2
, CH
4
and N
2
show favorable isotherms on both materials and the correlation using MPTA-DRA model is in good agreement with experimental results. The simulation of multicomponent sour natural gas adsorption indicates that almost none CH
4
and N
2
are adsorbed in conditions studied and that CO
2
and H
2
S compete for adsorption sites on both NaX and NaY. Partition coefficients of H
2
S are higher than CO
2
and increase from 18.90 to 43.30, for NaX, and from 4.04 to 27.39, for NaY, as CO
2
molar fraction in bulk phase decreases. The selectivity of H
2
S over CO
2
follows a different trend, decreasing from 27.16 to 20.14 for NaX and remaining somewhat constant around 4 for NaY. These results suggest higher selectivity for NaX when a lower CO
2
molar gas fraction is present. Meanwhile, for NaY, the CO
2
molar fraction does not influence the H
2
S/CO
2
selectivity. Therefore, simulations indicate that FAU NaX and NaY have good potential for natural gas sweetening at 4 MPa and 298 K
.
Understanding species‐environment relationships at large spatial scales is required for the prioritization of conservation areas and the preservation of landscape connectivity for large carnivores. ...This endeavour is challenging for jaguars (Panthera onca), given their elusiveness, and the local nature of most jaguar studies, precluding extrapolation to larger areas. We developed an occupancy model using occurrence data of jaguars across five countries of Central America, collected from camera‐trap studies of 2–12 months' duration, deployed over an area of 14 112 km2 from 2005 to 2018. Our occupancy model showed that habitat use of jaguars increased with primary net productivity and distance to human settlements, and distance to rivers. Detection of the species was related to survey effort and research team identity. Within the jaguar extent of occurrence, 73% was deemed suitable for the species, with 47% of it lying within Jaguar Conservation Units (JCU) and 59% of JCU land being legally protected. Suitable areas were divided into four distinct clusters of continuous habitat shared across country borders. However, large areas of predicted low habitat suitability may constrict connectivity in the region. The reliability of these spatial predictions is indicated by the model validation using an independent dataset (AUC = 0.82; sensitivity = 0.766, specificity = 0.761), and concordance of our results with other studies conducted in the region. Across Central America, we found that human influence has the strongest impact on jaguar habitat use and JCUs are the main reservoirs of habitat. Therefore, conservation actions must focus on preventing habitat loss and mitigating human pressure, particularly within the clusters of continuous areas of high suitability, and on restoring habitat to foster connectivity. The long‐term persistence of jaguars in the region will depend on strong international cooperation that secures jaguar populations and their habitat across Central American borders.
We developed an occupancy model using occurrence data of jaguars across five countries of Central America, collected from camera‐trap studies deployed over an area of 14 112 km2 from 2005 to 2018. Our occupancy model showed that human influence has the strongest impact on jaguar habitat use and JCUs are the main reservoirs of habitat. Therefore, conservation actions must focus on preventing habitat loss and mitigating human pressure, particularly within the clusters of continuous areas of high suitability, and on restoring habitat to foster connectivity.
In 2022, the European Chemicals Agency issued advice on the selection of high dose levels for developmental and reproductive toxicity (DART) studies indicating that the highest dose tested should aim ...to induce clear evidence of reproductive toxicity without excessive toxicity and severe suffering in parental animals. In addition, a recent publication advocated that a 10% decrease in body weight gain should be replaced with a 10% decrease in bodyweight as a criterion for dose adequacy. Experts from the European Centre for Ecotoxicology and Toxicology of Chemicals evaluated these recent developments and their potential impact on study outcomes and interpretation and identified that the advice was not aligned with OECD test guidelines or with humane endpoints guidance. Furthermore, data analysis from DART studies indicated that a 10% decrease in maternal body weight during gestation equates to a 25% decrease in body weight gain, which differs from the consensus of experts at a 2010 ILSI/HESI workshop. Dose selection should be based on a biological approach that considers a range of other factors. Excessive dose levels that cause frank toxicity and overwhelm homeostasis should be avoided as they can give rise to effects that are not relevant to human health assessments.
•ECHA's advice to increase dose levels in reproductive (DART) studies is evaluated.•Recommended high dose criteria contrary to OECD guidelines and DART experts' opinion.•Excessive dose levels may cause irrelevant secondary effects on reproduction.•Dose selection should consider the complexity of the maternal-placental-fetal model.
H
2
S and CO
2
are acid contaminants of natural gas and biogas, which removal have been studied using adsorption data for monocomponent and binary mixtures. However, equilibrium adsorption data for H
...2
S + CO
2
+ CH
4
mixture has not been investigated yet. In this work, H
2
S and CO
2
partition coefficients (K) and activated carbon (AC) selectivity (S) for H
2
S + CO
2
+ CH
4
mixture separation at high-pressure and different temperatures were determined. To reach this goal, monocomponent isotherms for H
2
S, CO
2
and CH
4
on Brazilian babassu coconut hush AC were experimentally determined at different temperatures and pressures. Then, obtained data were correlated by Langmuir and Tóth models, and multicomponent adsorption was predicted using Extended Langmuir, Extended Tóth and Ideal Adsorption Solution Theory (IAST) methods. Results indicate AC captures approximately 26 wt% of H
2
S or CO
2
. K values for CO
2
and H
2
S reached more than 3 and 26, respectively, depending on the predictive model utilized and were higher for diluted mixtures (high CH
4
content in gas phase). S values for CO
2
and H
2
S can reach values greater than 25 for Tóth + IAST. Furthermore, selectivity toward H
2
S is approximately 5.6 times greater than CO
2
. The effect of temperature on multicomponent results indicate K and S values decrease as temperature increases. Therefore, results obtained herein show that is possible to separate H
2
S and CO
2
from mixture containing CH
4
using this AC as adsorbent and better separation performance was observed for low H
2
S and CO
2
concentrations and lower temperatures.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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