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The configuration of a biologically fertile substrate for edible plant growth during long-term manned missions to Mars constitutes one of the main challenges in space research. Mars regolith amendment with compost derived from crew and crop waste in bioregenerative life support systems (BLSS) may generate a substrate able to extend crew autonomy and long-term survival in space. In this context, the aim of our work was threefold: first, to study the geochemistry and mineralogy of Mojave Mars Simulant (MMS-1) and the physico-chemical and hydraulic properties of mixtures obtained by mixing MMS-1 and green compost at varying rates (0:100, 30:70, 70:30, 100:0; v:v); secondly, to evaluate the potential use of MMS-1 as a growing medium of two lettuce (Lactuca sativa L.) cultivars; thirdly, to assess how compost addition may impact on sustainability of space agriculture by exploiting in situ resources. MMS-1 is a coarse-textured alkaline substrate consisting mostly of plagioclase, amorphous material and secondarily of zeolite, hematite and smectites. Although it can be a source of nutrients, it lacks organic matter, nitrogen, phosphorus and sulphur, which may be supplied by compost. Both cultivars grew well on all mixtures for 19 days under fertigation. Red Salanova lettuce produced a statistically higher dry biomass, leaf number and area than Green Salanova. Leaf area and plant dry biomass were the highest on 30:70 simulant:compost mixture. Nevertheless, the 70:30 mixture was the best substrate in terms of pore-size distribution for water-plant relationship and the best compromise for plant growth and sustainable use of compost, a limited resource in BLSS. Many remaining issues warrant further investigation concerning the dynamics of compost production, standardisation of supply during space missions and representativeness of simulants to real Mars regolith.

This study addresses the consequences of thermal radiation with slip boundary conditions and a uniform magnetic field on a steady 2D flow of trihybrid nanofluids over a spinning disc. The trihybrid nanocomposites are synthesized by the dispersion of aluminum oxide (Al2O3), zirconium dioxide (ZrO2), and carbon nanotubes (CNTs) in water. The phenomena are characterized as a nonlinear system of PDEs. Using resemblance replacement, the modeled equations are simplified to a nondimensional set of ODEs. The parametric continuation method has been used to simulate the resulting sets of nonlinear differential equations. Figures and tables depict the effects of physical constraints on energy and velocity profiles. According to this study, the slip coefficient enormously decreases the velocity field. For larger approximations of thermal radiation characteristics and heat source term boosts the thermal profile. This proposed model will assist in the field of meteorology, atmospheric studies, biological technology, power generation, automotive manufacturing, renewable power conversions, and detecting microchips. In regard to such kinds of practical applications, the proposed study is being conducted. This study is unique due to slip conditions and ternary fluid, and it could be used by other scholars to acquire further information about nanofluid thermal exchanger performance and stability.

Measurements made as part of the 1996 Yellow Sea experiment at location 37° N, 124° E, undertaken by China and the U.S. are analyzed. Signals generated by explosive sources were received by a 60-m-length vertical line array deployed in waters 75m deep. Evidence is presented that precursor arrivals measured at ranges less than 1km are refracted waves that are zeroth order in their ray series classification, and this directly points to the existence of a gradient in sediment sound speed. In contrast, first-order head waves, which are much weaker in amplitude, would exist only if this gradient were absent. It is found that the energy spectrum of precursor arrivals agrees well with a zeroth-order model, i.e., it is proportional to the source amplitude spectrum, S(f), where f is frequency, rather than a first-order model, which would have it proportional to S(f)∕f. From travel time analysis the sediment sound speed just below the water-sediment interface is estimated to be 1573m∕s with a gradient of 1.1s−1, and from analysis of the energy spectrum of the precursor arrivals the sediment attenuation is estimated to be 0.08dB∕m∕kHz over the frequency range 150–420Hz. The results apply to a nominal sediment depth of 100m.

Consider a situation where spatial heterogeneity leads to a cline, a gradual transition in dominance of two competing species. We first prove, in the context of a simplified competition–diffusion model, that there exists a stationary solution showing that the two species coexist in a transition zone. What happens then if, owing to climate change, the environmental profile moves with constant speed in space? We show here that, when the speed with which the environmental condition shifts exceeds the Fisher invasion speed of the advancing species, an expanding gap will form. We raise the question of whether such a phenomenon has been or can be observed.

AbstractThe wave load on potential offshore wind farms off Norway is studied by the use of a numerical wave refraction model. The model estimates trajectories of wave energy (rays) for waves propagating in water with varying surface velocity. The calculations indicate that for southerly and southwesterly winds the majority of shoreward propagating waves will converge in the coastal area off southwestern Norway. For offshore wave propagation directions equal to 180o and 210o, respectively 88% and 72% of the shoreward propagating rays approaches land south of Ålesund on the western part of Norway. For westerly and northerly winds the distributions are approximately uniform. It is further found that in the case of southerly or southwesterly winds, waves approach- ing the southern part of Norway are frequently misaligned with the wind. This will result in an increased bending moment of the masts. For offshore wave propagation direction between 180o and 240o the calculations indicate that approximately 24% of the rays reaching the coast of Norway along its southwestern part deviates by more than 45o of offshore propagation direction.

Currently, the PV solar sector represents approx. 2% of worldwide annual electricity production (https://webstore.iea.org/world-energy-outlook-2018), and therefore, is just at the verge of becoming visible in most countries. As the PV sector becomes increasingly visible to the next order of magnitude sometime in future, representing 20% in the electricity mix and beyond, it is now a good time to discuss reliability, predictability, and performance of PV power plants and as a consequence, the improvement potential for financial returns. Building on this train of thought, this article will provide a short introduction of PV power plant risks, predominantly related to technical performance. The question of risk mitigation measures will then be discussed: On the one side, quality assurance is a viable risk mitigation measure. However, even with quality assurance measures implemented, there are limitations when it comes to backstopping financial losses in the event that the performance deteriorates more than predicted and warranted by the manufacturers, or if the manufacturers or EPC's are no longer in business when incidental power degrades beyond calculated limits. Insurance solutions seem to provide an additional risk mitigation measure. Most insurance solutions on the market, however, only cover against externally induced risk exposures, e.g. severe weather, theft. Most of these insurance solutions follow a certain minimum standard. A few insurance products offer performance insurances where general cover is less standardized. All this triggers the question of how to look at insurance solutions. The interests of an insurance company are generally different than those of the insured stakeholders. These different viewpoints will be discussed, and selected warranty and insurance aspects will be considered. Recently, approximately 3500 insurance claim cases were statistically analyzed (http://www.pvstatlab.rwth-aachen.de/index.php/PVScan-project.html). Selected results of this analysis will be discussed. The article closes with an outlook of how insurers can likewise mitigate their risk exposure − in the end, insurers are only as good as the balance of the solvency resulting from their business model, or in the terminology of the insurance sector, the loss ratio must be at an acceptable level. This is where IECRE, the IEC System for Certification to Standards Relating to Equipment for Use in Renewable Energy Applications (https://www.iecre.org/), offering an international standard for certification − and in future − a rating system for PV power plants on a system level comes into play.

Abstract GeV–TeV gamma-rays and PeV–EeV neutrino backgrounds provide a unique window on the nature of the ultra-high-energy cosmic rays (UHECRs). We discuss the implications of the recent Fermi-LAT data regarding the extragalactic gamma-ray background and related estimates of the contribution of point sources as well as IceCube neutrino data on the origin of the UHECRs. We calculate the diffuse flux of cosmogenic γ-rays and neutrinos produced by the UHECRs and derive constraints on the possible cosmological evolution of UHECR sources. In particular, we show that the mixed-composition scenario considered in Globus et al., which is in agreement with both (i) Auger measurements of the energy spectrum and composition up to the highest energies and (ii) the ankle-like feature in the light component detected by KASCADE-Grande, is compatible with both the Fermi-LAT measurements and with current IceCube limits. We also discuss the possibility for future experiments to detect associated cosmogenic neutrinos and further constrain the UHECR models, including possible subdominant UHECR proton sources.